STATISTICAL ARTIFACTS IN THE RATIO OF DISCRETE QUANTITIES

The ratio is a familiar statistic, but it is often misused. One freque ntly overlooked problem occurs when ratioing two discrete (digitized) variables. Fine structure appears in the histogram of the ratio that c an be very subtle, or can sometimes even dominate the histogram. It di sappears when the numerator and/or denominator become continuous. This statistical artifact is not a binning error, nor is it removed by tak ing more data. It is important to be aware of the artifact in order to avoid misinterpretation of ratio data. We provide examples of the sta tistical artifact (including one from baseball) and discuss ways to av oid or minimize the problems it can cause.