The Reliability of Variables Measured as the Number of Events in an Interval of Time

In both the social and the natural sciences, many variables are measured as the number of events that occur in an interval of time. Recent sociological examples include the frequency of racial disturbances in American cities (Spilerman, 1970), the frequency of mental hospitalizations (Eaton, 1974), and the frequency of religious revivals in nineteenth-century Ohio counties (Hammond, 1974). Such measures often have several