How many accidents are needed to show a difference?
When a road safety study is contemplated one has establish how many accidents are needed to reach conclusions with a given level of confidence. Later, when the results are in, one has to be explicit about the confidence with which conclusions are stated. The purpose of this note is to describe a back-of-the envelope way of answering such questions with a precision that is sufficient for practical purposes.
Hauer
Ezra
E
Department of Civil Engineering, University of Toronto, 35 Merton Street, Toronto, Ontario, Canada. Ezra.Hauer@utoronto.ca
D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000465:Algorithms; D016001:Confidence Intervals; D006801:Humans; D015203:Reproducibility of Results