The Rule of Three
The rule of three states that if a certain event did not occur in a sample with
nsubjects, the interval from
3/nis a 95% confidence interval for the rate of occurrences in the population. When
nis greater than 30, this is a good approximation of results from more sensitive tests.
Eypasch, Ernst, et al. “Probability of adverse events that have not yet occurred: a statistical reminder.” Bmj 311.7005 (1995): 619-620.
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