Selection bias and individual differences are both potential problems dealing with the participants in a study.
a. Identify which of these is a threat to internal validity and which is a threat to external validity, and describe how each one is a threat.
b. Suppose that you were planning a research study in which the individuals who participate will be put into separate groups and each group will participate in one of the treatment conditions that are being compared. Explain how you could minimize the risk of selection bias and how you could minimize the risk that individual differences become a confounding variable.