Which term refers to a threat to internal validity due to differential dropout across treatment groups?

Which term refers to a threat to internal validity due to differential dropout across treatment groups?

• A. Attrition
• B. History effects
• C. Maturation
• D. Testing effects

Answer: (A)

Differential dropout between treatment groups threatens internal validity because when participants leave the study at different rates in each group, the groups being compared become unbalanced. This attrition can bias the estimated effect of the treatment since the remaining participants may differ in important ways from those who dropped out, leading to a comparison that no longer reflects what would happen if everyone stayed in the study. Other threats involve factors like external events affecting all groups (history), natural changes over time within participants (maturation), or changes in responses due to repeating measurements (testing). These do not specifically describe unequal dropout across groups, which is the defining issue here.

Differential dropout between treatment groups threatens internal validity because when participants leave the study at different rates in each group, the groups being compared become unbalanced. This attrition can bias the estimated effect of the treatment since the remaining participants may differ in important ways from those who dropped out, leading to a comparison that no longer reflects what would happen if everyone stayed in the study.

Other threats involve factors like external events affecting all groups (history), natural changes over time within participants (maturation), or changes in responses due to repeating measurements (testing). These do not specifically describe unequal dropout across groups, which is the defining issue here.