HOME-STUDY DRIVER EDUCATION
because they did not want the course to which they were assigned. Any bias in the study results caused by these students dropping out would be minimal given the very low dropout frequency.
Number (n) and Percentage of Students Who Enrolled in Each Instruction Method, Dropped Out, Did Not Complete the Course by the End of Data Collection, and
aDropout rates were not significantly different, χ2(3, N = 1,493) = 2.05, p = .56. bNon-completion rates higher for PEN and classroom than for the CD-ROM or workbook, χ2(3, N = 1,493) = 54.56, p < .05.
Of the 1,493 students who enrolled in the study, an additional 144 students (9.7%) did not finish the course to which they were assigned by the end of the data collection period (February 2003), as evidenced by their failure to complete the study exit exam. A chi square test of independence was used to determine if one type of course was completed more often than another. The results of the analysis showed statistically significant differences in the course completion rates among the instruction methods, χ2(3, N = 1,493) = 54.56, p < .05. These results indicate that a higher percentage of students assigned to classroom instruction, and an even higher percentage of students assigned to the PEN course, failed to complete their course compared to those assigned to either the CD-ROM or workbook instruction methods. There are likely qualitative differences (for example possible different motivation levels) between the students who did and did not complete each course. Any potential bias introduced into the study results by this difference would be expected to have a stronger effect on comparisons involving PEN (because PEN has the highest noncompletion rate), and to a lesser extent, classroom instruction. In particular, the high PEN non-completion rate may be a result of the PEN end-of-course test being difficult, which would result in less-able students being screened out from taking the study exit examination and DMV written test.
Data Analysis Strategy
The comparisons for the exit exam knowledge scores, exit exam attitude scores, and first-attempt DMV written test pass rates are based on the 1,321 students who completed the study exit examination. The participating driving schools and number of valid students from each school is shown in Appendix E. It was not possible to