Dietary Assessment Primer

Learn More about Calibration

In dietary assessment, the term "calibration" is used to refer to the re-scaling of dietary data obtained from a more biased, less accurate instrument using information obtained from a less biased, more accurate instrument (i.e., a [glossary term:] reference instrument). A calibrated instrument can be used to estimate population means and compare subpopulation means more [glossary term:] accurately than an instrument that has not been calibrated. Calibration is distinct from "[glossary term:] regression calibration," a term used to describe a method that uses calibration as part of a statistical procedure to better estimate associations (e.g., relative risks) between diet and other factors, such as health outcomes (Learn More about Regression Calibration).

Calibration can be used to relate reported intakes on a food frequency questionnaire (FFQ) or screener to a more accurate reference instrument administered in the same population ([glossary term:] internal calibration). For example, a study may administer an FFQ to all respondents and the reference instrument (such as 24-hour dietary recalls [24HR]) to a subsample. Alternatively, [glossary term:] external calibration using data from a reference population different from the study population can be performed. In this case, the external population should be similar to the study population. In both situations, [glossary term:] scoring algorithms are estimated and used to re-scale the dietary data from the screener (Learn More about Scoring Algorithms for Screeners). The use of such scoring algorithms for screeners has been shown to lead to estimates of mean intakes that are closer to means estimated with 24HR than those derived solely from screeners.

Calibration allows adjustment of estimates of the mean, but not the distribution. This is because the distribution of the calibrated instrument is typically narrower (has smaller variance) than the true distribution. Research is underway regarding the use of statistical modeling to estimate distributions (Learn More about Statistical Modeling).

For More Information

National Cancer Institute, Division of Cancer Control and Population Sciences, Applied Research Program. Dietary Screener Questionnaire in the NHANES 2009-10. (Accessed 6/16/14).

National Cancer Institute, Division of Cancer Control and Population Sciences, Applied Research Program. Short Dietary Assessment Instruments. (Accessed 6/16/14).

Thompson FE, Subar AF, Smith AF, Midthune D, Radimer KL, Kahle LL, Kipnis V. Fruit and vegetable assessment: performance of 2 new short instruments and a food frequency questionnaire. J Am Diet Assoc 2002 Dec;102(12):1764-72. [View Abstract]