A school district is comparing two reading programs for high school students reading below grade level. Two very similar schools are used to test the programs, a different one at each school. Students participating in the programs are pretested for their reading abilities and the mean scores are similar at both schools. The reading program implemented at High School A is known to be much more rigorous than the program implemented at High School B. The posttest shows more improvement at High School A, but more of the students dropped out of the program. What threat to internal validity does this pose?

1. how did conditions in germany and europe at the end of world war i contribute to the rise and triumph of nazism in germany? 2. how did the german government under nazi rule build support among the german people? 3. how did nazi germany gradually isolate, segregate, impoverish, and incarcerate jews and persecute other perceived enemies of the state between 1933 and 1939? 4. how did the nazis lead germany to war in europe and, with their collaborators, kill millions—including systematically murdering six million jewish people? 5. why is learning about the holocaust important? so we don’t repeat history.