Explain what “construct irrelevant variance” means in validity studies.

Construct irrelevant variance refers to the variance in test scores that does not pertain to the specific trait, ability, or quality that a test is intended to measure. In validity studies, it is crucial to isolate the true construct being assessed to ensure that the test results accurately reflect an individual's capabilities or potential. When construct irrelevant variance is present, it introduces extraneous factors that may influence test scores, which can lead to inaccurate assessments of an individual’s qualifications or competencies.

For instance, if a cognitive ability test is influenced by an unrelated factor such as anxiety or prior experience with the test format, the scores may not truly reflect the individual's cognitive abilities. This can result in decisions based on misleading information, which would compromise the test's validity.

Understanding construct irrelevant variance is essential for researchers and practitioners because it highlights the importance of designing tests that minimize this kind of variance, thereby increasing the accuracy and reliability of the assessments used in selection procedures.