Using natural frequencies to improve diagnostic inferences

  title={Using natural frequencies to improve diagnostic inferences},
  author={Ulrich Hoffrage and Gerd Gigerenzer},
  journal={Academic Medicine},
PURPOSE: To test whether physician's diagnostic inferences can be improved by communicating information using natural frequencies instead of probabilities. Whereas probabilities and relative frequencies are normalized with respect to disease base rates, natural frequencies are not normalized. METHOD: The authors asked 48 physicians in Munich and DÃsseldorf to determine the positive predictive values (PPVs) of four diagnostic tests. Information presented in the four problems appeared either as… 
Natural frequency trees improve diagnostic efficiency in Bayesian reasoning
Improving correctness and efficiency in Bayesian tasks might help to decrease overdiagnosis in daily clinical practice, which on the one hand cause cost and on the other hand might endanger patients' safety.
Natural Frequencies Do Not Foster Public Understanding of Medical Test Results
It is shown that natural frequencies may elicit evaluations that conflict with the normatively correct one, potentially hindering informed decision making and suggesting caution in promoting natural frequencies as the best way to communicate medical test data to health service users and patients.
Natural frequencies facilitate diagnostic inferences of managers
An implication of the work is that textbooks explaining Bayes’ rule should teach how to represent information in terms of natural frequencies instead of how to plug probabilities or percentages into a formula.
Natural Frequencies Help Older Adults and People with Low Numeracy to Evaluate Medical Screening Tests
Investigating whether natural frequencies facilitate accurate estimates in elderly people and whether performance depends on numeracy skills found that participants with higher numeracy scores performed better in the estimation tasks than those with lower numeracy Scores.
Improving Understanding of Health-Relevant Numerical Information
This chapter discusses why risks are often not communicated in a transparent and understandable way and why this is problematic, and illustrates, using an example from mammography screening, what transparent risk communication could look like.
Simple tools for understanding risks: from innumeracy to insight
A glance at the literature shows a shocking lack of statistical understanding of the outcomes of modern technologies, from standard screening tests for HIV infection to DNA evidence.
Natural frequencies improve Bayesian reasoning in simple and complex inference tasks
This work shows that natural frequencies facilitate Bayesian reasoning in a much broader class of situations than previously thought, and shows that teaching natural frequencies for simple tasks with one dichotomous cue and two hypotheses leads to a transfer of learning to complex tasks with three cue values and two cues.
Improving Diagnostic Efficiency with Frequency Double-Trees and Frequency Nets in Bayesian Reasoning
Frequency double-trees and frequency net diagrams help answer Bayesian tasks more accurately and also more quickly than the respective probability visualizations, and the effect of information format (probabilities v. frequencies) on performance is remarkably lower in this high-performing sample than that shown in previous studies.
Visualizing the Bayesian 2-test case: The effect of tree diagrams on medical decision making
In two studies, medical students from the University of Regensburg (Germany) with medical “2-test scenarios” were examined and it was found that natural frequency trees, especially when the question-related branches were highlighted, improved performance, but that none of the corresponding probabilistic visualizations did.


When doctors meet numbers.
How to Improve Bayesian Reasoning Without Instruction: Frequency Formats
By analyzing several thousand solutions to Bayesian problems, the authors found that when information was presented in frequency formats, statistically naive participants derived up to 50% of all inferences by Bayesian algorithms.
Interpretation by physicians of clinical laboratory results.
A small survey was conducted to obtain some idea of how physicians do, in fact, interpret a laboratory result, and asked if a test to detect a disease whose prevalence is 1/1000 has a false positive rate of .
AIDS counselling for low-risk clients.
This study addresses the counselling of heterosexual men with low-risk behaviour who, voluntarily or involuntarily, take an HIV test and proposes a simple method that counsellors can learn to communicate risks in a more effective way.
BasicBayes: A tutor system for simple Bayesian inference
Empirical evidence demonstrates the effectiveness of BasicBayes in teaching people simple Bayesian inference, and because of its flexible system architecture, it can also be used as a research tool.
The Empire of Chance: How Probability Changed Science and Everyday Life
This paper presents a probabilistic revolution in physics through the lens of inference, arguing that numbers rule the world and Chance and life: controversies in modern biology is a major controversy.
Th e psychology of good judgment: Frequency formats and simple algorithms
  • Journal of Medical Decision Making,
  • 1996
Probabilistic reasoning in clinical medicine: Problems and opportunities
  • 1982