What term refers to the variance that two or more tests share in common?

The term that refers to the variance that two or more tests share in common is covariance. Covariance measures how much two random variables vary together. In the context of tests, it indicates the degree to which the scores on the two tests change in relation to each other. A positive covariance means that as scores on one test increase, scores on the other test tend to increase as well, while a negative covariance suggests the opposite relationship.

Understanding covariance is crucial in research and program evaluation, particularly when assessing the relationship between different assessment tools or tests. It helps researchers identify if the tests are measuring similar constructs and contributes to the examination of reliability and validity in psychometric evaluations.

In contrast, variance denotes the extent to which scores vary within a single test, standard deviation is the square root of variance and represents data dispersion in the same unit as the original data, and reliability refers to the consistency of a test in measuring what it aims to measure. Each of these terms has distinct meanings and applications in research and evaluation methodologies.