Which test for comparing before/after and control groups?

dhundsness

New Member
Not sure which hypothesis tests would be best in these three scenarios:

1. Compare Before & After Scores
Students take a course, with a pre-test and a post-test. Is the course effective? e.g.:
...............People..Pre-test Avg..Post-test Avg
Population 1....30.........72%...........78%

2. Compare with Control Group
Some students take a new course. Everyone else takes the old course. They all take the same post-test. (No pre-test was taken.) Which course is more effective? e.g.:
..............People..Post-test Avg
Population 1....30........78%
Population 2....90........72%

3. Compare Before & After Scores with Control Group
Some students take a new course. Everyone else takes the old course. They all take the same pre-test and post-test. Which course is more effective? e.g.:
..............People..Pre-test Avg..Post-test Avg..Delta
Population 1....30........69%............78%........+9%
Population 2....90........66%............72%........+6%

This are just examples -- the population sizes and scores may vary. In all cases, individual scores are available for every student, if that produces better statistical results than just the group averages shown above. In #2 we must presume the student populations are drawn randomly. In #3 they are not random, and the pretest shows they are at different starting points.

Thanks for any insights you can give!