Validity is not a property of an instrument

A validated instrument is not a settled one. Validity is a judgment about whether scores mean what you think they mean, for these people, in this setting, for this purpose — change any of those and the judgment has to be made again. Content validity asks whether the items cover the construct and nothing else. Cognitive interviewing asks respondents what they thought a question meant, which is how you discover it was read differently than written. Item analysis asks which questions are doing work and which are filler.

Also covered: content validity · cognitive interviewing · item analysis · context dependence

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Read the chapter — Measurement and Construct Validation

Lesson 4 · 7 steps

1Even counting the dead takes judgment5:59 2From conceptual model to measurement6:14 3Finding good indicators5:04 4Indexes and scales6:44 5Validity is not a property of an instrument7:43 6Factor analysis and reliability10:27 7Does it match reality, and does it travel?5:45

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The Validity Toolkit · lesson 4 of 4