Key Concepts about Validation

Note: Because Validation and Measurement Error are closely related concepts in dietary assessment using self-report instruments and are equally important to being able to conduct research using these instruments, we suggest that you read both Key Concepts sections of the Primer in tandem. You may also wish to work with a statistician in applying the concepts described here.

Validation in dietary assessment is conducted to determine how accurately self-report instruments measure [glossary term:] true intakes. Two main types of designs are used in validation studies:

A key goal of all validation research is to use an unbiased reference measure or instrument that captures true intake without systematic error. Known unbiased reference measures include recovery biomarkers and data from feeding studies or direct observation, but few such measures are available and/or feasible [2]. Therefore, dietary assessment instruments are often evaluated using as a reference another self-report instrument thought to capture diet with systematic bias, but with less bias than the instrument being evaluated (the main instrument). We refer to such instruments as imperfect references. For example, 24-hour dietary recalls (24HRs) are an example of an imperfect [glossary term:] reference instrument used for validating food frequency questionnaires (FFQs).