Exhibit 11-4.Identify the major threat to internal validity in the following research studies.
-Refer to Exhibit 11-4.A researcher used two classrooms in an experimental study.It was found that the E group had more high ability students than the C group before the study began.
A) Regression
B) Diffusion
C) Mortality
D) Selection
E) History

Question

Quizplus · Accepted Answer

The major threat to internal validity in this study is selection, as the researcher did not randomly assign students to the two classrooms and instead had pre-existing groups with different levels of abilities. This means that differences found between the E and C groups may be due to their pre-existing differences rather than the treatment being studied.