Exhibit 11-4

Multiple Choice

Exhibit 11-4.Identify the major threat to internal validity in the following research studies.
-Refer to Exhibit 11-4.A teacher researcher randomly assigned students within a classroom to two groups, one of which received some special instructional materials to take home with them to study and to use with homework assignments.The C group did not get the special materials.The researcher was surprised to find that there weren't significant differences between the two groups on achievement tests and other selected measures.

A) Regression
B) Diffusion
C) Mortality
D) Selection
E) History