A single-sample procedure is given for selecting the least probable event in a multinomial distribution. Given two numbers $(c, P^\ast)$, it is required to determine the smallest sample size for which the probability of a correct selection is at least as large as $P^\ast$ when the (unknown) difference between the smallest and the next smallest cell probabilities is greater than or equal to $c$. A table is given showing the required sample size for specified values of $c$ and $P^\ast$.
"On Selecting the Least Probable Multinomial Event." Ann. Math. Statist. 43 (6) 1981 - 1990, December, 1972. https://doi.org/10.1214/aoms/1177690870