A Nurse Who Is Reading a Research Report Has Questions

A nurse who is reading a research report has questions about the study's internal validity. Which questions might this nurse be considering?. Select all that apply.

A) Was there bias in the random selection of study subjects?
B) Was the research setting adequately controlled?
C) Do all of the items being measured focus on the same trait?
D) Did the independent variable occur before the dependent variable?
E) Why was the sample size at the end of the study so much smaller than the sample size at the beginning of the study?