Fig. 2. Rounding interval influenced the goodness-of-fit P value for two common tests of normality: the Lilliefors test (open circle) and Shapiro–Wilk test (open triangle). The test data series was an ideal log-normal distribution (n = 50; mean = 30 min; SD = 10 min) rounded to the nearest 1-, 3-, 5-, 10-, or 15-min interval and log transformed before testing.