Which of the Following Is Not an Example of a Nonexperimental

Which of the following is not an example of a nonexperimental or quasi-experimental study?

A) a study comparing self-esteem scores for children with a learning disability versus scores for children without a learning disability
B) a study comparing depression scores before therapy versus scores after therapy
C) a study comparing performance in a room where the walls have been painted yellow versus performance in a room painted blue
D) a study comparing attitude scores for men versus scores for women