To establish the reliability and validity of an existing measurement tool, what should the evaluator conduct?

When evaluating the reliability and validity of an existing measurement tool, conducting an item analysis is a crucial step. Item analysis involves examining the individual items or questions within the measurement tool to determine how well they function in terms of measuring the intended constructs. This process includes assessing the difficulty level of items, the discrimination index (how well an item differentiates between high and low performers), and overall item effectiveness in contributing to the tool's validity and reliability.

Through item analysis, evaluators can gather statistical data that reveals whether each item performs consistently across different administrations and if it accurately measures the underlying concept. This ensures that the tool is both reliable (producing consistent results over time) and valid (accurately assessing what it intends to measure).

In contrast, while other options like norm-referenced tests and criterion-referenced tests also assess aspects of measurement tools, they serve different purposes. Norm-referenced tests compare an individual’s performance against a group, and criterion-referenced tests measure specific skills or knowledge against a set standard, but neither directly involves the analysis of individual items for performance refinement. A semantic differential survey is a specific assessment technique used to measure attitudes and does not focus on the reliability or validity of an existing measurement tool in the same way.