Lead times will vary slightly from stock order to stock order and at various times of the year with fluctuations resulting from business activity, vacation schedules, transportation and numerous other factors. Selecting a lead time for Poisson use, which represents a pure average of actual stock order lead times, is not appropriate. Rather, the table selected should be based on the maximum reasonable total lead time … i.e., the lead time table used should satisfy approximately 90% or better of all actual stock order lead times.