Identify the threats to internal validity. (A) Selection threat (B) Maturation…

Concept

Internal validity asks whether a study's observed effect can be attributed to the intervention rather than to alternative explanations.

Threats to internal validity are design or process factors that can create such alternative explanations, including pre-existing group differences, natural change, participant loss, and testing effects.

Application

• Selection can create pre-existing differences between the groups being compared.

• Maturation can change participants naturally over the course of a study.

• Attrition can alter the composition of groups when participants leave the study.

• Testing can change later performance because earlier measurement affects participants.

Contrast

• The combination of selection, maturation, and attrition leaves out testing.

• The combination of maturation, attrition, and testing leaves out selection.

• The combination of selection, attrition, and testing leaves out maturation.

• The combination containing selection, maturation, attrition, and testing covers every named threat.

Result

Therefore, selection, maturation, attrition, and testing are all threats to internal validity; the accepted combination contains all four named threats.