The "Unusual Episode" Data Revisited

A certain dataset, giving population at risk and fatalities for "an unusual episode," has been used for some time in classrooms as an elementary exercise in statistical thinking, the challenge being to deduce the context of the data. Unfortunately, the "solution" has frequently been circulated orally, with few details. Moreover, discrepancies have been found between the dataset and the "solution," which would render the exercise somewhat artificial. This paper investigates the discrepancies and includes a fully-explained version of the dataset for classroom use.