Update a diagnostic probability after a test result

Reinforce Bayes order from clinical-decision or reliability training. Treatment or scrap is not decided from sensitivity alone; prior and likelihood must be combined first.

1. State the prior probability from prevalence or history.
2. Obtain the test’s sensitivity and false-positive rate.
3. Apply Bayes to get the posterior given this result.
4. Compare the posterior to the decision threshold.
5. Act only after that comparison.
6. Do not treat a ‘positive test’ as certainty when the prior is very low.