Post-test probability
Enter valid values, then select Calculate.
Evidence tools
Practical tools for evaluating clinical evidence.
Convert a pre-test probability and likelihood ratio into a post-test probability, then use a structured checklist to examine the evidence and governance behind a clinical AI system.
Educational use only. These tools are not medical advice or clinical decision support. Do not enter names, identifiers, health records or other patient information. Verify all inputs, outputs and assumptions independently.
Bayesian update
Post-test probability calculator.
Enter a pre-test probability as a percentage and a likelihood ratio for one finding or test result.
Calculation method
The calculator converts probability to odds, applies the likelihood ratio, then converts the result back to probability.
- pre-test odds = p ÷ (1 − p)
- post-test odds = pre-test odds × LR
- post-test p = post-test odds ÷ (1 + post-test odds)
Assumptions matter. A likelihood ratio is transferable only when the finding, threshold, test quality, setting and patient spectrum are sufficiently comparable to the source evidence. Sequential multiplication can be misleading when findings are not conditionally independent.
Clinical AI evaluation
Questions to ask before relying on a system.
Mark only items you have verified from appropriate documentation or evidence. The count measures checklist completion, not system quality, safety or regulatory status.
Use the underlying records. Product copy, a certification logo or a single benchmark score cannot answer this checklist on its own. Review the intended-use statement, model card, validation report, privacy and security documentation, regulatory position and local clinical-governance requirements.
Privacy by design
No clinical record belongs in these tools.
The calculator needs only two numeric values, and the checklist needs only local checkbox state. The tools do not submit form entries or request a server response.
No account
Neither tool requires sign-in, a name, an email address or an organisation.
No saved result
Selections and calculations remain in the current page and are cleared by reset or reload.
No patient input
Use abstract numeric values and system documentation only. Do not paste or infer patient information.
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