Which validity indicates the degree to which performance on one test correlates with performance on a second test?

The concept being discussed is concurrent validity, which refers to the extent to which the results of one test correlate with the results of another test that measures the same construct at the same time. This type of validity is particularly important when we want to assess the accuracy or relevance of a new test by comparing it with a pre-existing, established measure.

For example, if a new assessment tool for mathematical skills is developed, concurrent validity can be demonstrated by showing a strong correlation between the scores on this new tool and the scores on a well-established math test given to the same group of students. A high correlation would indicate that both tests are measuring the same underlying ability effectively, supporting the validity of the new assessment.

In contrast, predictive validity is concerned with how well a test can predict future performance, reliability refers to the consistency of a test's results over time, and construct validity assesses how well a test truly measures the theoretical construct it claims to measure. Understanding these distinctions helps clarify why concurrent validity specifically focuses on the relationship between two tests taken around the same timeframe.