Measuring centre: the mean: mean = add all values of observation and divide it by the number of observations, x-bar, is not resistant to influence of extreme measures not a resistant measure. Comparing the mean and the median: median is resistant if distribution is exactly symmetric, mean and median are the same in skewed distribution, mean is usually farther out in the long tail than median. ~for ny travel time data, iqr = 27. 5. 1. 5 x iqr = 1. 5 x 27. 5 = 41. 25. Q1 (1. 5 x iqr) = 15. 0 41. 25 = -26. 25 and. Q3 + (1. 5 x iqr) = 42. 5 + 41. 25 = 83. 75. Looking at example 2. 3, only suspected outlier is longest travel time, 85 mins. The 1. 5xiqr rules state that the three next longest travel times (60, 65mins) are just part of the long right tail of this skewed distribution. Once you know what to look for, you can read output form any technological tool .