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. 2023 May 16;2(1):e000399.
doi: 10.1136/bmjmed-2022-000399. eCollection 2023.

Defining representativeness of study samples in medical and population health research

Jacqueline E Rudolph  1 , Yongqi Zhong  1 , Priya Duggal  1 , Shruti H Mehta  1 , Bryan Lau  1
Affiliations

Defining representativeness of study samples in medical and population health research

Jacqueline E Rudolph et al. BMJ Med. .

Abstract

Medical and population health science researchers frequently make ambiguous statements about whether they believe their study sample or results are representative of some (implicit or explicit) target population. This article provides a comprehensive definition of representativeness, with the goal of capturing the different ways in which a study can be representative of a target population. It is proposed that a study is representative if the estimate obtained in the study sample is generalisable to the target population (owing to representative sampling, estimation of stratum specific effects, or quantitative methods to generalise or transport estimates) or the interpretation of the results is generalisable to the target population (based on fundamental scientific premises and substantive background knowledge). This definition is explored in the context of four covid-19 studies, ranging from laboratory science to descriptive epidemiology. All statements regarding representativeness should make clear the way in which the study results generalise, the target population the results are being generalised to, and the assumptions that must hold for that generalisation to be scientifically or statistically justifiable.

Keywords: Epidemiology; Public health; Research design; Statistics.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/ and declare: support from the National Institutes of Health for the submitted work; all authors declare no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1
Example where a study sample (which is a simple random sample of the target population) is representative because its results generalise in interpretation and in estimate. Shaded box=treatment group; hashed lines=outcome group. Colours represent different levels of an effect measure modifier on the risk difference scale, which did not affect selection into the study sample
Figure 2
Figure 2
Example where a study sample (which is a convenience sample of the target population) is representative because its results generalise in interpretation even though they do not generalise in estimate. Shaded box=treatment group; hashed lines=outcome group. Colours represent different levels of an effect measure modifier on the risk difference scale, which affected selection into the study sample
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