Which of the following threats to internal validity are associated primarily…

Concept

Internal validity asks whether an observed effect can be attributed to the treatment rather than to another cause. Participant-related threats arise from who enters the groups, what happens to participants while the study runs, or who remains in the sample.

Application

Selection concerns systematic differences in the participants assigned to comparison groups. History concerns outside events experienced by participants during the study, and attrition concerns participants leaving the study. These three threats therefore arise through participant composition, experience, or retention.

Contrast

• Testing threat: repeated exposure to a test or measure can influence later scores; its immediate source is the testing procedure.

• Selection threat: pre-existing differences between participant groups can imitate a treatment effect.

• History threat: events occurring during the study can change participants independently of the treatment.

• Attrition threat: participant loss can change the composition of the groups being compared.

Result

The participant-associated threats are Selection, History, and Attrition; therefore, the accepted combination is (B), (C), and (D) only.