Statistical methods for comparing two or more injury incidence rates a
re presented as an aid in selecting operations for ergonomic intervent
ion to reduce work place injuries. The methods assume that injuries oc
cur according to a Poisson process and the analysis is conditional on
the total number of injuries. Methods presented include hypothesis tes
ts to compare the ratio of two injury incidence rates and hypothesis t
ests to compare more than two rates. The power of these comparisons in
creases with the total number of injuries observed, the Type I error p
robability, and as the ratio of the injury exposure periods approaches
one. Expressions for simultaneous confidence intervals for two or mor
e rates and for the ratios of two or more rates are also given. These
general statistical methods can be implemented easily on a personal co
mputer.