Laypersons' understanding of statistical concepts commonly used in prescription drug promotion: A review of the research literature

Background: The prevalence of direct-to-consumer (DTC) advertising for prescription drugs has led to concerns about how consumers interpret the medical information conveyed in these ads. One strategy for improving lay understanding of medical information involves incorporating quantitative information about a treatment's potential benefits and risks. Objective: This literature review investigates laypersons' interpretations of statistical concepts, expanding on past reviews and including terms that may be used in DTC prescription drug advertising. Methods: We searched six databases for articles published from January 2000 to October 2021. Articles were included if they were in English and examined general or lay audiences' comprehension of quantitative or statistical concepts, without limiting the context of the studies to medical situations. Results: We identified 25 eligible articles. The evidence suggests that likelihood ratios, odds ratios, probabilities, numbers needed to treat/harm, and confidence intervals hinder comprehension of quantitative information. The results are mixed for information presented as frequencies, percentages, absolute risk reduction, and relative risk reduction. The mixed findings could be due to numeracy, framing as risks or benefits, and operationalization of the outcomes. We found no studies examining interpretations of minimum, maximum, central tendency, power, statistical significance, or hazard ratio. Conclusion: Studies spanning several decades have examined how laypeople interpret statistical concepts. While a few terms are consistently studied, many questions still remain on how to make risk information more understandable to lay audiences, particularly those with low numeracy.