If a researcher runs an ad in a paper in order to recruit subjects, and places the first 10 people who call in one group and the next 10 people who call in another group, what sort of threat to internal validity has been introduced?
A) Mortality
B) Experimenter bias
C) Selection bias
D) Regression effect

Question

Quizplus · Accepted Answer

Selection bias has been introduced because the researcher is not randomly assigning participants to groups. The groups are being formed based on who calls in first, which could result in the two groups being different from each other before any manipulation or intervention has even occurred.

If a Researcher Runs an Ad in a Paper in Order