Likelihood Ratio Probability Explorer
Explore how a specified likelihood ratio changes a hypothetical pretest probability.
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Explore Bayes’ rule using an explicitly chosen pretest probability and a likelihood ratio for one test result. Educational scenario only; do not use this tool to diagnose an individual. All default values are fictional.
Calculation results
Post-test probability: 50%
Assumptions and limits
Pretest odds = p/(1−p); post-test odds = pretest odds × LR; probability = odds/(1+odds). Choose LR+ for a positive result or LR− for a negative result from applicable diagnostic evidence. An LR is a nonnegative ratio, not sensitivity or specificity. LR=1 leaves probability unchanged. An assumed pretest probability, biased accuracy study or unsuitable reference standard makes the result unreliable. Do not multiply LRs from dependent tests without justification. Uncertainty intervals and treatment thresholds are not calculated. Exact 0% or 100% and LR=0 are mathematical boundary scenarios, not established clinical certainty.