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Content experts frequently are used in the judgment-quantification stage of content validation of instruments. However, errors in instrumentation may arise when important steps in selecting and using these experts are not carefully planned. The systematic process of choosing, orienting, and using content experts in the judgment-qualification stage of instrument development is addressed, with particular attention to the often neglected, important step of familiarizing these experts with the conceptual underpinnings and measurement model of the instrument. An example using experts to validate content for a measure of caregiver burden is used to illustrate this stage of instrument review.

Reliability assessments are appropriate for each research instrument in a study. Measures of internal consistency are a popular set of assessments with Cronbach's alpha being the most favored. Two other measures of internal consistency, theta and omega, have particular characteristics that make their use desirable under certain circumstances. Each of these three measures and its computation is described and examples provided.