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1.  The effect of cash and other financial inducements on the response rate of general practitioners in a national postal study. 
BACKGROUND: Low response rates are acknowledged as a potential source of bias in survey results. Response rates are a particular problem in surveys of GPs. Thus, the methods used to encourage response to mailed surveys and the influence of inducements in maximizing response rates are fundamental issues to be examined when addressing the problem of response bias. AIM: To increase the overall response rate to a national study of GPs and to explore the effects of financial and non-financial inducements on response rates. METHODS: Two mailing waves of a postal questionnaire to a 20% random sample of all GPs in England and Wales had achieved a 33% response rate. For the third mailing wave, the non-responding GPs were then divided into a control group, a group who were offered a donation to charity to complete the questionnaire and a group who were offered cash. The charity and cash groups were further subdivided into 5 pounds and 10 pounds groups to assess the effect of the size of the inducement offered. For the control group, a fourth wave was sent the offer of a 5 pounds or 10 pounds incentive. RESULTS: Response was positively affected by the offer of an inducement. Cash, however, had a more substantial effect than the offer of a donation to charity. Older GPs were less likely to participate overall, whereas male GPs were more likely to respond to a cash inducement. Doctors who had seen more patients were less likely to reply earlier and were more likely to respond to the offer of cash. CONCLUSIONS: Primary care is going through many changes, some of which have increased the workload of the GP. It may now be that, to achieve the response rates needed to validate policy-related research, the offer of inducements will become a necessary part of the research process.
PMCID: PMC1312912  PMID: 9101691
2.  Comparison of response rates and cost-effectiveness for a community-based survey: postal, internet and telephone modes with generic or personalised recruitment approaches 
Epidemiological research often requires collection of data from a representative sample of the community or recruitment of specific groups through broad community approaches. The population coverage of traditional survey methods such as mail-outs to residential addresses, and telephone contact via public directories or random-digit-dialing is declining and survey response rates are falling. There is a need to explore new sampling frames and consider multiple response modes including those offered by changes in telecommunications and internet technology.
We evaluated response rates and cost-effectiveness for three modes of survey administration (postal invitation/postal survey, postal invitation/internet survey and postal invitation/telephone survey) and two styles of contact approach (personalised and generic) in a community survey of greywater use. Potential respondents were contacted only once, with no follow up of non-responders.
The telephone survey produced the highest adjusted response rate (30.2%), followed by the personalised postal survey (10.5%), generic postal survey (7.5%) and then the internet survey (4.7% for the personalised approach and 2.2% for the generic approach). There were some differences in household characteristics and greywater use rates between respondents to different survey modes, and between respondents to personalised and generic approaches. These may be attributable to the differing levels of motivations needed for a response, and varying levels of interest in the survey topic among greywater users and non-users. The generic postal survey had the lowest costs per valid survey received (Australian $22.93), followed by the personalised postal survey ($24.75).
Our findings suggest that postal surveys currently remain the most economic option for population-based studies, with similar costs for personalised and generic approaches. Internet surveys may be effective for specialised groups where email lists are available for initial contact, but barriers other than household internet access still exist for community-based surveys. Given the increasing recruitment challenges facing community-based studies, there is an imperative to gather contemporary comparative data on different survey modes and recruitment approaches in order to determine their strengths, limitations and costs. Researchers also need to document and report on the potential biases in the target and respondent populations and how this may affect the data collected.
PMCID: PMC3502082  PMID: 22938205
Survey methods; Postal survey; Telephone survey; Internet survey; Cost-effectiveness
3.  The Effect of Low Survey Response Rates on Estimates of Alcohol Consumption in a General Population Survey 
PLoS ONE  2012;7(4):e35527.
Response rates for surveys of alcohol use are declining for all modes of administration (postal, telephone, face-to-face). Low response rates may result in estimates that are biased by selective non-response. We examined non-response bias in the NZ GENACIS survey, a postal survey of a random electoral roll sample, with a response rate of 49.5% (n = 1924). Our aim was to estimate the magnitude of non-response bias in estimating the prevalence of current drinking and heavy episodic (binge) drinking.
We used the “continuum of resistance” model to guide the investigation. In this model the likelihood of response by sample members is related to the amount of effort required from the researchers to elicit a response. First, the demographic characteristics of respondents and non-respondents were compared. Second, respondents who returned their questionnaire before the first reminder (early), before the second reminder (intermediate) or after the second reminder (late) were compared by demographic characteristics, 12-month prevalence of drinking and prevalence of binge drinking.
Demographic characteristics and prevalence of binge drinking were significantly different between late respondents and early/intermediate respondents, with the demographics of early and intermediate respondents being similar to people who refused to participate while late respondents were similar to all other non-respondents. Assuming non-respondents who did not actively refuse to participate had the same drinking patterns as late respondents, the prevalence of binge drinking amongst current drinkers was underestimated. Adjusting the prevalence of binge drinkers amongst current drinkers using population weights showed that this method of adjustment still resulted in an underestimate of the prevalence.
The findings suggest non-respondents who did not actively refuse to participate are likely to have similar or more extreme drinking behaviours than late respondents, and that surveys of health compromising behaviours such as alcohol use are likely to underestimate the prevalence of these behaviours.
PMCID: PMC3332039  PMID: 22532858
4.  Do incentives, reminders or reduced burden improve healthcare professional response rates in postal questionnaires? two randomised controlled trials 
Healthcare professional response rates to postal questionnaires are declining and this may threaten the validity and generalisability of their findings. Methods to improve response rates do incur costs (resources) and increase the cost of research projects. The aim of these randomised controlled trials (RCTs) was to assess whether 1) incentives, 2) type of reminder and/or 3) reduced response burden improve response rates; and to assess the cost implications of such additional effective interventions.
Two RCTs were conducted. In RCT A general dental practitioners (dentists) in Scotland were randomised to receive either an incentive; an abridged questionnaire or a full length questionnaire. In RCT B non-responders to a postal questionnaire sent to general medical practitioners (GPs) in the UK were firstly randomised to receive a second full length questionnaire as a reminder or a postcard reminder. Continued non-responders from RCT B were then randomised within their first randomisation to receive a third full length or an abridged questionnaire reminder. The cost-effectiveness of interventions that effectively increased response rates was assessed as a secondary outcome.
There was no evidence that an incentive (52% versus 43%, Risk Difference (RD) -8.8 (95%CI −22.5, 4.8); or abridged questionnaire (46% versus 43%, RD −2.9 (95%CI −16.5, 10.7); statistically significantly improved dentist response rates compared to a full length questionnaire in RCT A. In RCT B there was no evidence that a full questionnaire reminder statistically significantly improved response rates compared to a postcard reminder (10.4% versus 7.3%, RD 3 (95%CI −0.1, 6.8). At a second reminder stage, GPs sent the abridged questionnaire responded more often (14.8% versus 7.2%, RD −7.7 (95%CI −12.8, -2.6). GPs who received a postcard reminder followed by an abridged questionnaire were most likely to respond (19.8% versus 6.3%, RD 8.1%, and 9.1% for full/postcard/full, three full or full/full/abridged questionnaire respectively). An abridged questionnaire containing fewer questions following a postcard reminder was the only cost-effective strategy for increasing the response rate (£15.99 per response).
When expecting or facing a low response rate to postal questionnaires, researchers should carefully identify the most efficient way to boost their response rate. In these studies, an abridged questionnaire containing fewer questions following a postcard reminder was the only cost-effective strategy. An increase in response rates may be explained by a combination of the number and type of contacts. Increasing the sampling frame may be more cost-effective than interventions to prompt non-responders. However, this may not strengthen the validity and generalisability of the survey findings and affect the representativeness of the sample.
PMCID: PMC3508866  PMID: 22891875
5.  Increasing response to a postal survey of sedentary patients – a randomised controlled trial [ISRCTN45665423] 
A systematic review identified a range of methods, which can influence response rates. However, analysis specific to a healthcare setting, and in particular, involving people expected to be poor responders, was missing, We examined the effect of pre-warning letters on response rates to a postal survey of sedentary patients whom we expected a low rate of response.
Participants were randomised to receive a pre-warning letter or no pre-warning letter, seven days before sending the main questionnaire. The main questionnaire included a covering letter and pre-paid return envelope. After seven days, non-responders were sent a reminder letter and seven days later, another reminder letter with a further copy of the questionnaire and return envelope.
627 adults, with a mean age of 48 years (SD 13, range 18 to 78) of whom 69.2% (434/627) were women, were randomised. 49.0% (307/627) of patients were allocated to receive a pre-warning letter and 51.0% (320/627) no pre-warning letter, seven days in advance of posting the main questionnaire. The final response rate to the main questionnaire was 30.0% (92/307) amongst those sent a pre-warning letter and 20.9% (67/320) not sent a pre-warning letter, with an adjusted odds ratio of 1.60 (95% CI 1.1, 2.30).
The relatively low cost method of sending a pre-warning letter had a modest impact on increasing response rates to a postal questionnaire sent to a group of patients for whom a low response rate was anticipated. Investigators should consider incorporating this simple intervention when conducting postal surveys, to reduce the potential for nonresponse bias and to increase the study power. Methods other than postal surveys may be needed however when a low response rate to postal surveys is likely.
PMCID: PMC534787  PMID: 15537429
6.  Accuracy of responses from postal surveys about continuing medical education and information behavior: experiences from a survey among German diabetologists 
Postal surveys are a popular instrument for studies about continuing medical education habits. But little is known about the accuracy of responses in such surveys. The objective of this study was to quantify the magnitude of inaccurate responses in a postal survey among physicians.
A sub-analysis of a questionnaire about continuing medical education habits and information management was performed. The five variables used for the quantitative analysis are based on a question about the knowledge of a fictitious technical term and on inconsistencies in contingency tables of answers to logically connected questions.
Response rate was 52%. Non-response bias is possible but seems not very likely since an association between demographic variables and inconsistent responses could not be found. About 10% of responses were inaccurate according to the definition.
It was shown that a sub-analysis of a questionnaire makes a quantification of inaccurate responses in postal surveys possible. This sub-analysis revealed that a notable portion of responses in a postal survey about continuing medical education habits and information management was inaccurate.
PMCID: PMC126225  PMID: 12153701
7.  Effect of numbering of return envelopes on participation, explicit refusals, and bias: experiment and meta-analysis 
Tracing mail survey responses is useful for the management of reminders but may cause concerns about anonymity among prospective participants. We examined the impact of numbering return envelopes on the participation and the results of a survey on a sensitive topic among hospital staff.
In a survey about regrets associated with providing healthcare conducted among hospital-based doctors and nurses, two randomly drawn subsamples were provided numbered (N = 1100) and non-numbered (N = 500) envelopes for the return of completed questionnaires. Participation, explicit refusals, and item responses were compared. We also conducted a meta-analysis of the effect of questionnaire/envelope numbering on participation in health surveys.
The participation rate was lower in the “numbered” group than in the “non-numbered” group (30.3% vs. 35.0%, p = 0.073), the proportion of explicit refusals was higher in the “numbered” group (23.1% vs 17.5%, p = 0.016), and the proportion of those who never returned the questionnaire was similar (46.6% vs 47.5%, p = 0.78). The means of responses differed significantly for 12 of 105 items (11.4%), which did not differ significantly from the expected frequency of type 1 errors, i.e., 5% (permutation test, p = 0.078). The meta-analysis of 7 experimental surveys (including this one) indicated that numbering is associated with a 2.4% decrease in the survey response rate (95% confidence interval 0.3% to 4.4%).
Numbered return envelopes may reduce the response rate and increase explicit refusals to participate in a sensitive survey. Reduced participation was confirmed by a meta-analysis of randomized health surveys. There was no strong evidence of bias.
PMCID: PMC3898011  PMID: 24428941
Health surveys; Survey participation; Survey numbering; Bias; Sensitive topic; Meta-analysis
8.  Surveying general practitioners: does a low response rate matter? 
BACKGROUND: Primary care has long been of interest to policy research. Recently, there is evidence to suggest that it is becoming more difficult to encourage GPs (general practitioners) to participate in surveys. As low response rates can introduce bias into survey results, it is important to study the effects of non-response. AIM: To assess the validity of a response rate of 44% obtained in a national postal study of GPs surveyed about their work with alcohol-misusing patients by assessing the extent of any non-response bias. METHOD: A telephone survey of 148 GPs who had not responded to repeated mailings of a postal questionnaire was undertaken. In addition to personal and practice structure characteristics, the GPs were asked three questions taken from the original questionnaire about their work with alcohol-misusing patients. RESULTS: Of the 148 GPs telephoned, 64 responded to the telephone questionnaire in full; all had previously failed to respond to the postal questionnaire. Younger GPs were more likely to respond to both the national postal and telephone surveys, but more so to the latter. Telephone responders were more likely to be GPs in a single-handed practice. The work of GPs with alcohol-misusing patients highlighted differences between the two response groups. Male telephone responders were found to be identifying a significantly higher average of alcohol misusers than male postal responders. Telephone responders were more likely to feel trained in treating alcohol misuse and to feel better supported to deal with this patient group. CONCLUSION: Some significant differences were identified, indicating the presence of non-response bias. A low response rate need not affect the validity of the data collected, but it is still necessary to test for non-response effects and make corrections to the original data in order to maximize validity.
PMCID: PMC1312913  PMID: 9101692
9.  'So much post, so busy with practice--so, no time!': a telephone survey of general practitioners' reasons for not participating in postal questionnaire surveys. 
The British Journal of General Practice  1998;48(428):1067-1069.
BACKGROUND: Response rates by general practitioners (GPs) to postal surveys have consistently fallen, compromising the validity of this type of research. If postal survey work is to continue we need to understand GPs' reasons for not participating and respond appropriately. AIM: To investigate GPs' reasons for not responding to postal surveys. METHOD: A qualitative study was carried out to determine GPs reasons for not participating in postal surveys, which were drawn from a telephone survey of 276 non-responders to a postal questionnaire survey. Practitioners' comments were recorded and reasons for their non-response quantified using content analysis. RESULTS: Primary reasons for GPs not replying to the postal survey were that questionnaires had got lost in paperwork (34%), that GPs were too busy for the extra work involved (21%), and that questionnaires were routinely 'binned' (16%). Higher practice workloads, including increased administration, meant that participation in research had become a low priority. GPs provided some suggestions for researchers that would increase their chances of questionnaires being returned. CONCLUSIONS: Researchers need to be aware of the pressures of service general practice and to rationalize the amount of research material sent to GPs. GPs were most likely to respond to postal surveys that had a high interest factor, that involved localized research relevant to general practice, and that incorporated a personalized approach by researchers, including good-quality explanatory information.
PMCID: PMC1410021  PMID: 9624749
10.  Impact of a postcard versus a questionnaire as a first reminder in a postal lifestyle survey. 
STUDY OBJECTIVE--The study aimed to consider the impact of two different types of reminder on response rates and costs in a postal survey. DESIGN--The study was a cross sectional survey. A self-completion lifestyle questionnaire was used. Those who did not respond after the initial mailing were randomly allocated to receive either a postcard or questionnaire as a first reminder. All outstanding non-responders received a questionnaire as a second reminder. SUBJECTS--A representative sample of 698 adults aged 16-70 was used, drawn from a family health services authority register. MAIN RESULTS--Postcard reminders were as effective as questionnaire reminders in increasing response whether one or two reminders are sent. The costs per response were calculated. Two questionnaires as reminders were found to be 1.7 times more expensive than a postcard plus questionnaire. Including the initial mailing, the cost per response using all questionnaires was 1.3 times the cost when a postcard was used for the first reminder. CONCLUSIONS--To increase the response to a postal survey effectively and economically, two reminders should be sent--first a postcard and then a questionnaire.
PMCID: PMC1059805  PMID: 8228774
11.  International health policy survey in 11 countries: assessment of non-response bias in the Norwegian sample 
International health policy surveys are used to compare and evaluate health system performance, but little is known about the effects of non-response. The objective of this study was to assess the effects of non-response in the Norwegian part of the Commonwealth Fund international health policy survey in 2009.
As part of an international health policy survey in 2009 a cross-sectional survey was conducted in Norway among a representative sample of Norwegian general practitioners. 1 400 randomly selected GPs were sent a postal questionnaire including questions about the Norwegian health care system, the quality of the GPs' own practice and the cooperation with specialist health care. The survey included three postal reminders and a telephone follow-up of postal non-respondents. The main outcome measures were increase in response rate for each reminder, the effects of demographic and practice variables on response, the effects of non-response on survey estimates, and the cost-effectiveness of each reminder.
After three postal reminders and one telephone follow-up, the response rate was 59.1%. Statistically significant differences between respondents and non-respondents were found for three variables; group vs. solo practice (p = 0.01), being a specialist or not (p < 0.001) and municipality centrality (least central vs. most central, p = 0.03). However, demographic and practice variables had little association with five outcome variables and the overall survey estimates changed little with additional reminders. In addition, the cost-effectiveness of the final reminders was poor.
The response rate in the Norwegian survey was satisfactory, and the effect of non-response was small indicating adequate representativeness. The cost-effectiveness of the final reminders was poor. The Norwegian findings strengthen the international project, but restrictions in generalizability warrant further study in other countries.
PMCID: PMC2833149  PMID: 20146819
12.  Effect of questionnaire length, personalisation and reminder type on response rate to a complex postal survey: randomised controlled trial 
Minimising participant non-response in postal surveys helps to maximise the generalisability of the inferences made from the data collected. The aim of this study was to examine the effect of questionnaire length, personalisation and reminder type on postal survey response rate and quality and to compare the cost-effectiveness of the alternative survey strategies.
In a pilot study for a population study of travel behaviour, physical activity and the environment, 1000 participants sampled from the UK edited electoral register were randomly allocated using a 2 × 2 factorial design to receive one of four survey packs: a personally addressed long (24 page) questionnaire pack, a personally addressed short (15 page) questionnaire pack, a non-personally addressed long questionnaire pack or a non-personally addressed short questionnaire pack. Those who did not return a questionnaire were stratified by initial randomisation group and further randomised to receive either a full reminder pack or a reminder postcard. The effects of the survey design factors on response were examined using multivariate logistic regression.
An overall response rate of 17% was achieved. Participants who received the short version of the questionnaire were more likely to respond (OR = 1.48, 95% CI 1.06 to 2.07). In those participants who received a reminder, personalisation of the survey pack and reminder also increased the odds of response (OR = 1.44, 95% CI 1.01 to 1.95). Item non-response was relatively low, but was significantly higher in the long questionnaire than the short (9.8% vs 5.8%; p = .04). The cost per additional usable questionnaire returned of issuing the reminder packs was £23.1 compared with £11.3 for the reminder postcards.
In contrast to some previous studies of shorter questionnaires, this trial found that shortening a relatively lengthy questionnaire significantly increased the response. Researchers should consider the trade off between the value of additional questions and a larger sample. If low response rates are expected, personalisation may be an important strategy to apply. Sending a full reminder pack to non-respondents appears a worthwhile, albeit more costly, strategy.
PMCID: PMC3110121  PMID: 21548947
13.  Non-response in a nationwide follow-up postal survey in Finland: a register-based mortality analysis of respondents and non-respondents of the Health and Social Support (HeSSup) Study 
BMJ Open  2012;2(2):e000657.
To examine difference in mortality between postal survey non-respondents and respondents.
A prospective cohort study with baseline survey in 1998 and comprehensive linkage to national mortality registers until 2005, the Health and Social Support study.
A population-based postal survey of the working-aged population in Finland in 1998.
The original random sample comprised 64 797 working-aged individuals in Finland (20–24, 30–34, 40–44, 50–54 years of age; 32 059 women and 32 716 men), yielding 25 898 (40.0%) responses in the baseline postal survey in 1998.
Primary outcome measure
Registry-based primary causes of death encoded with the International Classification of Diseases (ICD-10).
In women, HR for total mortality was 1.75 (95% CI 1.40 to 2.19) times higher among the non-respondents compared with the respondents. In men, non-response was associated with a 1.41-fold (1.21–1.65) excess risk of total mortality. Non-response associated in certain age groups with deaths due to diseases in women and with deaths due to external causes in men. The most prominent excess mortality was seen for total mortality for both genders and for mortality due to external causes among men.
Postal surveys result in slight underestimation of illness prevalence.
Article summary
Article focus
Women and individuals from upper social strata tend to participate more actively in postal health surveys.
What this exactly means in terms of health selection among respondents is unclear.
Postal health surveys are believed to produce underestimates of illness prevalence.
Key messages
Total mortality was consistently and for women in the age group ≥50 years and for men in the age groups ≥40 years significantly higher among non-respondents compared with respondents during a 7-year follow-up among a total Finnish nationwide sample in working age comprising almost 65 000 individuals.
The excess mortality observed was 1.5–2 fold. Among men, it was explained by external causes, whereas among women, it was due to diseases and was statistically significant only in the age group 50–54 years.
Postal surveys result in slight underestimation of illness prevalence.
Strengths and limitations of the study
The linkage to mortality data was successful for virtually all individuals of the original sample comprising nearly 65 000 individuals. The sample size secures the reliability of the conclusions drawn. Furthermore, the registry data on mortality in Finland can be considered as reliable. To the best of the authors' knowledge, a corresponding study based on an as large a sample as in this study has not previously been carried out.
Some inaccuracy concerning the final diagnosis of death is possible. A further study limitation is that data of socioeconomic status or educational level of non-respondents were not available, and hence, adjustments of the statistical analyses for these variables were not possible.
PMCID: PMC3307122  PMID: 22422917
14.  A randomised controlled trial of postal versus interviewer administration of a questionnaire measuring satisfaction with, and use of, services received in the year before death 
STUDY OBJECTIVES: To develop a short form of an interview schedule used successfully in previous national surveys of care for the dying, and to investigate the effect of administering it by post on response rate, response bias and on the nature of responses to questions. DESIGN: Randomised controlled trial. SETTING: An inner London health authority. PARTICIPANTS: Informants (person registering death) of random sample of cancer deaths between June 1995 and July 1996. MAIN RESULTS: The shortened questionnaire (VOICES) has 158 questions. Response rate did not differ significantly between postal and interview groups (interview; 56% (69 of 123), postal: 52% (161 of 308). Responders in the two groups did not differ in terms of their sociodemographic characteristics. Postal questionnaires had significantly more missing data, particularly on questions about service provision and satisfaction with services. Responses to questions differed between the groups on 11 of 158 questions. Interview group respondents were more likely to give top ranking responses to questions on service satisfaction and symptom control. CONCLUSIONS: Postal questionnaires are an acceptable alternative to interviews in retrospective post- bereavement surveys of care for the dying, at least in terms of response rate and response bias. However, the increased costs of interview surveys need to be balanced against the fact that postal questionnaires result in more missing data, and possibly less reliable answers to some questions. Caution is needed in combining results from the two data collection methods as interview respondents gave more positive answers to some questions.
PMCID: PMC1756658  PMID: 10396521
15.  Gift Card Incentives and Non-Response Bias in a Survey of Vaccine Providers: The Role of Geographic and Demographic Factors 
PLoS ONE  2011;6(11):e28108.
This study investigates the effects of non-response bias in a 2010 postal survey assessing experiences with H1N1 influenza vaccine administration among a diverse sample of providers (N = 765) in Washington state. Though we garnered a high response rate (80.9%) by using evidence-based survey design elements, including intensive follow-up and a gift card incentive from Target, non-response bias could exist if there were differences between respondents and non-respondents. We investigated differences between the two groups for seven variables: road distance to the nearest Target store, practice type, previous administration of vaccines, region, urbanicity, size of practice, and Vaccines for Children (VFC) program enrollment. We also examined the effect of non-response bias on survey estimates. Statistically significant differences between respondents and non-respondents were found for four variables: miles to the nearest Target store, type of medical practice, whether the practice routinely administered additional vaccines besides H1N1, and urbanicity. Practices were more likely to respond if they were from a small town or rural area (OR = 7.68, 95% CI = 1.44−40.88), were a non-traditional vaccine provider type (OR = 2.08, 95% CI = 1.06−4.08) or a pediatric provider type (OR = 4.03, 95% CI = 1.36−11.96), or administered additional vaccines besides H1N1 (OR = 1.80, 95% CI = 1.03−3.15). Of particular interest, for each ten mile increase in road distance from the nearest Target store, the likelihood of provider response decreased (OR = 0.73, 95% CI = 0.60−0.89). Of those variables associated with response, only small town or rural practice location was associated with a survey estimate of interest, suggesting that non-response bias had a minimal effect on survey estimates. These findings show that gift card incentives alongside survey design elements and follow-up can achieve high response rates. However, there is evidence that practices farther from the nearest place to redeem gift cards may be less likely to respond to the survey.
PMCID: PMC3223226  PMID: 22132224
16.  Factors Associated With African-American and White Elders’ Participation in a Brain Donation Program 
This study examined factors associated with brain donation program participation among African-American and White elders. By postal mail, participants were recruited from an Alzheimer’s research registry (all of whom had been invited to participate in the Center’s brain donation program) and asked to complete surveys assessing brain donation knowledge, trust in healthcare systems, and religiousness. African-American respondents completed a cultural mistrust inventory. Demographic, brain donation status, and literacy data (as assessed by the Wide Range Achievement Test-3 Reading subtest) were compiled from the respondents’ most recent registry visit. The survey response rate was 60% (n=184 White and n=49 Black respondents). Logistic regression, comparing religiousness, trust in healthcare institutions, and educational attainment, identified a single predictor (ie, religiousness) in the prediction of donation status among White respondents (P=0.008), whereas no predictors were observed for donation status among the Black respondents. Using all African-American donors and nondonors from the registry (n=68), comparisons revealed Wide Range Achievement Test-3 Reading score differences for African-American donors (46.8±5.9) and nondonors (42.8±8.4, P=0.02). Results suggest that increased religiousness is related to White elders’ decisions not to donate, whereas lower reading ability might be related to African-American participants’ decisions not to donate.
PMCID: PMC3010335  PMID: 20856099
African-American; brain donation; cultural mistrust; religiousness; research participation
17.  Physiotherapy Practice and Delegation Policies in Oxygen Administration: A Survey of Ontario Hospitals 
Physiotherapy Canada  2009;61(3):163-172.
Purpose: As of 2008, the Regulated Health Professions Act in Ontario stipulates that administration of oxygen is a controlled act, which physiotherapists are not authorized to perform but which may be delegated to physiotherapists by another health professional authorized to perform this act. The aims of this study were (1) to survey physiotherapy practice of oxygen administration in Ontario hospitals and (2) to determine the proportion and characteristics of hospitals with delegation policies for physiotherapists to administer oxygen.
Method: Postal surveys were sent to 208 hospitals. Data were collected on hospital characteristics; the presence of delegation policies; and the practice and training of physiotherapists, physiotherapy assistants, and students in oxygen administration. Data were described by summative statistics. Fisher's exact test and Cramer's V statistic were used to examine associations. Potential prognostic factors were analyzed using logistic regression.
Results: Response rate was 82.7%. Physiotherapists administered oxygen in 39% of hospitals, and 28% of hospitals had delegation policies. Larger, urban, or teaching hospitals and those with a matrix structure were most likely to have delegation policies and physiotherapists who administered oxygen. Rehabilitation hospitals were also likely to have such policies.
Conclusion: Physiotherapists administer oxygen in less than half of Ontario hospitals, very few of which have delegation policies.
PMCID: PMC2787575  PMID: 20514179
best practice; delegation policy; oxygen administration; physiotherapist; Regulated Health Professions Act; scope of practice; titration; administration d'oxygène; cadre des fonctions; Loi sur les professions de la santé réglementées; physiothérapeute; politique de délégation; pratique exemplaire; titrage
18.  Investigating non-response bias in mail surveys. 
Losses in follow-up that are biased with respect to outcome invalidate the results. There are many ways of dealing with non-response in follow-up studies. Three separate methods were used to investigate a potential bias in a mail survey of 2471 disabled people. At a response rate of 84%, the non-respondents were significantly different from the respondents with respect to the outcome, return to work and vocational training. The success rate in terms of the outcome was negatively related to the number of reminders. Significant differences were found in response rates according to age, social class, impairments, previous employment record, and completion of rehabilitation courses. There is no safe level of response rates below 100%. However small the non-response, a possible bias as a result of it must be investigated.
PMCID: PMC1052180  PMID: 6461711
19.  General Practitioners' views on the provision of nicotine replacement therapy and bupropion 
Nicotine replacement therapies (NRT) and a new drug, bupropion, are licensed in several countries as aids to smoking cessation. General practitioners (GPs) play a crucial role in recommending or prescribing these medications. In the UK there has been discussion about whether the medications should be reimbursable by the National Health Service (NHS). This study assessed English GPs' attitudes towards reimbursement of NRT and bupropion.
Postal survey of a randomly selected national sample of GPs; 376 GPs completed the questionnaire after one reminder; effective response rate: 53%. There was no difference between the responses of GPs who responded to the initial request and those who responded only after a reminder suggesting minimal bias due to non-response.
Attitudes of GPs were remarkably divided on most issues relating to the medications. Forty-three percent thought that bupropion should not be on NHS prescription while 42% thought that it should be (15% did not know); Fifty percent thought that NRT should not be on NHS prescription while 42% thought it should be (8% did not know). Requiring that smokers attend behavioural support programmes to be eligible to receive the medications on NHS prescription made no appreciable difference to the GPs' views. GPs were similarly divided on whether having the medications reimbursable would add unacceptably to their workload or offer a welcome opportunity to discuss smoking with their patients. A principal components analysis of responses to the individual questions on NRT and bupropion revealed that GPs' attitudes could be understood in terms of a single 'pro-con' dimension accounting for 53% of the total variance which made no distinction between the two medications.
GPs in England appear to be divided in their attitudes to medications to aid smoking cessation and appear not to discriminate in their views between different types of medication or different aspects of their use. This suggests that their attitudes are generated by quite fundamental values. Addressing these values may be important in encouraging GPs to adhere more closely to national and international guidelines.
PMCID: PMC59675  PMID: 11701091
20.  The requirement for prior consent to participate on survey response rates: a population-based survey in Grampian 
A survey was carried out in the Grampian region of Scotland with a random sample of 10,000 adults registered with a General Practitioner in Grampian. The study complied with new legislation requiring a two-stage approach to identify and recruit participants, and examined the implications of this for response rates, non-response bias and speed of response.
A two-stage survey was carried out consistent with new confidentiality guidelines. Individuals were contacted by post and asked by the Director of Public Health to consent to receive a postal or electronic questionnaire about communicating their views to the NHS. Those who consented were then sent questionnaires. Response rates at both stages were measured.
25% of people returned signed consent forms and were invited to complete questionnaires. Respondents at the consent stage were more likely to be female (odds ratio (OR) response rate of women compared to men = 1.5, 95% CI 1.4, 1.7), less likely to live in deprived postal areas (OR = 0.59, 95% CI 0.45, 0.78) and more likely to be older (OR for people born in 1930–39 compared to people born in 1970–79 = 2.82, 95% CI 2.36, 3.37). 80% of people who were invited to complete questionnaires returned them. Response rates were higher among older age groups. The overall response rate to the survey was 20%, relative to the original number approached for consent (1951/10000).
The requirement of a separate, prior consent stage may significantly reduce overall survey response rates and necessitate the use of substantially larger initial samples for population surveys. It may also exacerbate non-response bias with respect to demographic variables.
PMCID: PMC293468  PMID: 14622444
21.  Investigating non-response bias in a survey of disablement in the community: implications for survey methodology. 
STUDY OBJECTIVE--The aim was to investigate the pattern of age specific non-response bias in a two phase survey of disablement in the community. It seeks to examine patterns of response in different age groups to a household based postal questionnaire, and the implication of such trends for the estimation of prevalence of reported dependence. It also looks at the effect that the readiness to respond during the first phase postal questionnaire had on participation in the interview based second phase of the study. DESIGN AND SETTING--A two stage survey of disablement in the population was undertaken. A first phase postal questionnaire was sent to 25,168 households in Calderdale, West Yorkshire, England, to ascertain the prevalence of physical disability. The second phase comprised in depth interviews with a sample of individuals identified in the first phase as being disabled. RESPONDENTS--A total of 21,889 postal questionnaires were returned (87%) representing households containing 42,826 people aged 16 years and over. A disproportionately stratified random sample of 950 respondents reporting disability was taken for the second phase. Of these 891 were still available, and 838 (94%) were interviewed. MEASUREMENTS AND MAIN RESULTS--A study of the timing of response to a postal questionnaire showed that patterns differed for different age groups. The estimated prevalence of those aged 65 years and over who were dependent was steady over time whereas for those in the 16-64 age range the estimated prevalence fell as the survey progressed, indicating a tendency for those who were dependent to respond sooner. Examination of the relationship of responses at phase 1 and phase 2 showed that response to invitation to interview was much less in those who had responded later, and presumably more reluctantly, in the first phase. CONCLUSIONS--These findings raise questions about how different patterns of response might be indicative of bias which could differentially affect final age specific prevalence estimates. They also have methodological implications for the follow up of reluctant responders both to increase the response rate and to secure cooperation in the second phase of a two phase survey.
PMCID: PMC1060767  PMID: 1836811
22.  Nonresponse Error in Mail Surveys: Top Ten Problems 
Nursing Research and Practice  2011;2011:987924.
Conducting mail surveys can result in nonresponse error, which occurs when the potential participant is unwilling to participate or impossible to contact. Nonresponse can result in a reduction in precision of the study and may bias results. The purpose of this paper is to describe and make readers aware of a top ten list of mailed survey problems affecting the response rate encountered over time with different research projects, while utilizing the Dillman Total Design Method. Ten nonresponse error problems were identified, such as inserter machine gets sequence out of order, capitalization in databases, and mailing discarded by postal service. These ten mishaps can potentiate nonresponse errors, but there are ways to minimize their frequency. Suggestions offered stem from our own experiences during research projects. Our goal is to increase researchers' knowledge of nonresponse error problems and to offer solutions which can decrease nonresponse error in future projects.
PMCID: PMC3169191  PMID: 21994846
23.  The Effects of Tracking Responses and the Day of Mailing on Physician Survey Response Rate: Three Randomized Trials 
PLoS ONE  2011;6(2):e16942.
The response rates to physician postal surveys remain modest. The primary objective of this study was to assess the effect of tracking responses on physician survey response rate (i.e., determining whether each potential participant has responded or not). A secondary objective was to assess the effects of day of mailing (Monday vs. Friday) on physician survey response rate.
We conducted 3 randomized controlled trials. The first 2 trials had a 2×2 factorial design and tested the effect of day of mailing (Monday vs. Friday) and of tracking vs. no tracking responses. The third trial tested the effect of day of mailing (Monday vs. Friday). We meta-analyzed these 3 trials using a random effects model.
The total number of participants in the 3 trials was 1339. The response rate with tracked mailing was not statistically different from that with non-tracked mailing by the time of the first reminder (RR = 1.01 95% CI 0.84, 1.22; I2 = 0%). There was a trend towards lower response rate with tracked mailing by the time of the second reminder (RR = 0.91; 95% CI 0.78, 1.06; I2 = 0%). The response rate with mailing on Mondays was not statistically different from that with Friday mailing by the time of first reminder (RR = 1.01; 95% CI 0.87, 1.17; I2 = 0%), and by the time of the 2nd reminder (RR = 1.08; 95% CI 0.84, 1.39; I2 = 77%).
Tracking response may negatively affect physicians' response rate. The day of mailing does not appear to affect physicians' response rate.
PMCID: PMC3044144  PMID: 21373197
24.  A randomised controlled trial to determine the effect on response of including a lottery incentive in health surveys [ISRCTN32203485] 
Postal questionnaires are an economical and simple method of data collection for research purposes but are subject to non-response bias. Several studies have explored the effect of monetary and non-monetary incentives on response. Recent meta-analyses conclude that financial incentives are an effective way of increasing response rates. However, large surveys rarely have the resources to reward individual participants. Three previous papers report on the effectiveness of lottery incentives with contradictory results. This study aimed to determine the effect of including a lottery-style incentive on response rates to a postal health survey.
Randomised controlled trial. Setting: North and West Birmingham. 8,645 patients aged 18 or over randomly selected from registers of eight general practices (family physician practices). Intervention: Inclusion of a flyer and letter with a health questionnaire informing patients that returned questionnaires would be entered into a lottery-style draw for £100 of gift vouchers. Control: Health questionnaire accompanied only by standard letter of explanation. Main outcome measures: Response rate and completion rate to questionnaire.
5,209 individuals responded with identical rates in both groups (62.1%). Practice, patient age, sex and Townsend score (a postcode based deprivation measure) were identified as predictive of response, with higher response related to older age, being female and living in an area with a lower Townsend score (less deprived).
This RCT, using a large community based sample, found that the offer of entry into a lottery style draw for £100 of High Street vouchers has no effect on response rates to a postal health questionnaire.
PMCID: PMC534094  PMID: 15533256
25.  A selective follow-up study on a public health survey 
Background: The non-response rates in surveys are increasing which is problematic as it means that a progressively smaller proportion of the population represents the majority, and it is uncertain how health survey results are affected. This follow-up was performed on the non-responders to the postal questionnaire in the public health survey Life and Health, conducted in Örebro County Council, Sweden, where large differences in response rates had been found between different socio-demographic groups and geographical areas. The main objective was to analyse non-response bias regarding self-rated health. Methods: This follow-up study was conducted as a census to all non-responders in the area that had the lowest response rate and, in one other geographical area used as a control. It was carried out by telephone interviews, 49.3% (580 individuals) answered the follow-up. The outcome variable was self-rated health, a main variable in public health surveys. Differences in response patterns between responders and initial non-responders were approximated by prevalences with confidence intervals and adjusted odds ratios. Results: Poor health was more common in the initial non-response group than among the responders, even with consideration given to sex, age, country of birth and education. However, good health was equally common among responders and initial non-responders. Conclusions: Public health surveys can be biased due to certain groups being under-represented or not represented at all. For this reason, in repeated public health surveys, we recommend selective follow-ups of such groups at regular intervals.
PMCID: PMC3553586  PMID: 22253457

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