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Risk expression using likelihood ratios and natural frequencies in Bayesian inference tasks-a preregistered
Philipp Schulz1, Odette Wegwarth1,2, Helge Giese3
1Heisenberg Chair for Medical Risk Literacy & Evidence-Based Decisions, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany.
BMC Medical Education
|April 9, 2025
Summary
Medical students better understand sequential diagnostic tests using odds and likelihood ratios (odds/LR). Natural frequencies are superior for single tests, but odds/LR improve interpretation of multiple tests for clinical decision-making.
Area of Science:
- Medical Education
- Diagnostic Test Interpretation
- Clinical Decision-Making
Background:
- Medical students require strong diagnostic test interpretation skills for informed decision-making.
- Natural frequencies are standard for single diagnostic tests but may be less effective for sequential testing.
- This study investigates odds and likelihood ratios (odds/LR) as an alternative for sequential diagnostic test interpretation.
Purpose of the Study:
- To compare the effectiveness of natural frequencies versus odds/LR for calculating positive predictive values (PPV) of single and sequential diagnostic tests.
- To assess the subjective comprehensibility of these two formats among students.
Main Methods:
- A randomized-controlled crossover trial involving 167 medical and 162 psychology students.
- Participants calculated PPVs for single and sequential diagnostic tests using either natural frequencies or odds/LR.
- Primary outcome: proportion of correctly calculated PPVs; Secondary outcome: subjective comprehensibility.
Main Results:
- Natural frequencies yielded higher correct PPVs for single tests (36.2% vs 21.6%).
- Odds/LR resulted in significantly more correct PPVs for sequential tests (10.6% vs 4.9%).
- Students found natural frequencies more comprehensible than odds/LR.
Conclusions:
- Odds/LR may enhance medical students' understanding of sequential diagnostic tests.
- Integrating odds/LR alongside natural frequencies could improve diagnostic decision-making skills.
- Further education on odds/LR can benefit medical students' interpretation of complex diagnostic scenarios.
Keywords:
Bayesian reasoningConditional probabilitiesNatural frequenciesOddsPositive predictive valueMore Related Videos
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