Find P90, which is the pulse rate separating the bottom 90% from the top 10%. Female Pulse Rates. In Exercises 13–20, assume that an adult female is randomly selected. Females have pulse rates that are normally distributed with a mean of 74.0 beats per minute and a standard deviation of 12.5 beats per minute (based on Data Set 1 “Body Data” in Appendix B). (Hint: Draw a graph in each case.)