When,from the outset of an experiment,differences exist between the kinds of individuals in one group and those in another group,there is a potential threat to internal validity called
A) contamination.
B) attrition.
C) selection.
D) additive effect of selection and history.

Question

Quizplus · Accepted Answer

When there are differences in the kinds of individuals in the different groups, there is a selection threat to internal validity. This means that the groups are not equivalent at the start of the study, which can lead to biased results. Contamination refers to when the treatment spills over into the control group, attrition refers to when participants drop out of the study, and an additive effect of selection and history refers to when the two threats combine to influence the results.

When,from the Outset of an Experiment,differences Exist Between the Kinds