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"1-in-X" Bias: "1-in-X" format causes overestimation of health-related risks

Sirota, M and Juanchich, M and Bonnefon, JF (2018) '"1-in-X" Bias: "1-in-X" format causes overestimation of health-related risks.' Journal of Experimental Psychology: Applied, 24 (4). 431 - 439. ISSN 1076-898X

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© 2018 American Psychological Association. According to the "1-in-X" effect, "1-in-X" ratios (e.g., 1 in 12) trigger a higher subjective probability than do numerically equivalent "N-in-X*N" ratios (e.g., 3 in 36). Here we tested the following: (a) the effect on objective measures, (b) its consequences for decision-making, (c) whether this effect is a form of bias by measuring probability accuracy, and (d) its amplification in people with lower health literacy and numeracy. In parallel-designed experiments, 975 participants from the general adult population participated in 1 of 5 experiments following a 2(format: "1-in-X" or "N-in-X*N") * 4(scenarios) mixed design. Participants assessed the risk of contracting a disease on either a verbal probability scale (Experiment 1) or a numerical probability/frequency scale with immediate (Experiments 2-3) or delayed presentation (Experiments 4-5). Participants also made a health-related decision and completed a health literacy and numeracy scale. The "1-in-X" ratios yielded higher probability perceptions than did the "N-in-X*N" ratios and affected relevant decisions. Critically, the "1-in-X" ratios led to a larger objective overestimation of numerical probabilities than did the "N-in-X*N" ratios. People with lower levels of health literacy and numeracy were not more sensitive to the bias. Health professionals should use "1-in-X" ratios with great caution when communicating to patients, because they overestimate health risks.

Item Type: Article
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Divisions: Faculty of Science and Health > Psychology, Department of
Depositing User: Elements
Date Deposited: 23 Jul 2018 13:32
Last Modified: 15 Apr 2019 23:15

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