You have just learned of survey results conducted by your university on the drinking behaviors of the college campus. Wondering about the results, you ask yourself the following questions: how were participants selected, were participants selected depending on if they lived on or off campus, were all the participants in a sorority or fraternity, were non–traditional age students included in the survey, and were men and women equally sampled? These types of questions indicate that you are concerned about what threat to internal validity?
