At the pre- and post-test dates the sample size was 61. At the follow-up test the sample size was 35. Some participants dropped out due to scheduling problems.
To look for an effect of practice with the groups collapsed, paired t-tests compared trials 1 and 2 at each set of tests at each test date. For obstacles no significant differences were found between test pairs at the pre- (t=(60)=0.14 p=0.9), post- (t(60)=0.7, p=0.5) or follow-up test (t(34)=0, no p-value), i.e. trials when lenses were not worn. For time pre-test trial 1 took significantly longer than trial 2, (t(60)=2.9, p=0.005) but at the post-test (t(60)=.64, p=0.5) and follow-up test (t(34)=1.1, p=0.2) trials 1 and 2 did not differ significantly. Obstacles were significantly greater at trial 1 than trial 2 at the transfer test (t(60)=3.3, p=0.002) but not at the retention test (t(34)=−1.1, p=0.3). Time was significantly greater at trial 1 than trial 2 at the transfer test (t(60)=3.5, p<0.0008) and at the retention test (t(34)=6.9, p< 0.01). Therefore, since the second trial may have yielded a practice effect on trials when lenses were worn, subsequent analyses used only data from Trial 1. See and .
Descriptive statistics of the number of obstacles touched at each test date. For each trial values given are mean (standard deviation), [median (range)].
Descriptive statistics of the time (sec) to complete the course at each test date. For each trial values given are mean (standard deviation) [range].
Repeated measures analysis of variance (ANOVA) of Trial 1 pre-, post- and follow-up test scores by obstacles was significant for test dates (F(2, 32)=6.1, p=0.004) but not for the Date by Group interaction (F(2, 4, 64)=1.6, p=0.2). Post-hoc Bonferroni-corrected t-tests showed significantly fewer obstacles at post- than pre-test (t (60)=2.6, p=0.01) and fewer obstacles at the pre- than follow-up test (t(34)=3.6, p=0.001). Post-hoc Bonferroni-corrected t-tests of the difference between post- and follow-up tests were not significant. These data suggested a learning effect over test dates in trials without lenses. ANOVA of trial 1 pre-, post- and follow-up tests scores by time was significant for test dates (F(2,32)=4.0, p=0.02) and for the Date by Group interaction (F(2, 4, 64)=3.3, p=0.02). Post-hoc Bonferroni-corrected t-tests showed slightly but significantly shorter times at the post- than the pre-test (t(60)=3.0, p=0.003), also suggesting a slight learning effect. No other differences were found between test dates with groups collapsed. These findings supported our hypothesis about repeated testing.
ANOVA showed no significant differences among groups at the pre-test for time (F(2, 57)=2.5, p=0.1) or obstacles (F(2, 57)=0.1, p=0.9), at the post-test for time (F(2, 57)=2.8, p=0.7), or at the follow-up test for time (F(2, 57)=2.2, p=0.1) or obstacles (F(2, 57)=0.5, p=0.6). The ANOVA at the post-test was significant for obstacles (F(2, 57)=4.1, p=0.3). Post-hoc Fisher Least Significant Difference (FLSD) tests showed a significant difference between the sham and single lens groups (p=0.009), indicating that the single lens group hit significantly fewer obstacles than the sham group. No other differences were found for tests performed without lenses. See and .
ANOVA by group, was not significant for time at either the transfer test (F(2)=1.0, p=0.4) or the retention test (F(2)=0.8, p=0.4. ANOVA by group for obstacles at the transfer test was significant (F (2) = 4.5, p=0.02). The significant post-hoc FLSD showed that the multiple lens group touched significantly fewer obstacles than the sham group (p< 0.02). At the retention test, the ANOVA was nonsignificant (F(2)=2.6, p=0.08). See and .