The Differences Among Methods for Computation of Quartiles Do Matter

Darja Rupnik Poklukar and Janez Zerovnik

University of Ljubljana, Faculty of Mechanical Engineering, Askerceva 6, SI-1000 Ljubljana, Slovenia

Abstract: The choice of the method for computation of quartiles may have a direct impact on practical decisions. As the differences among the methods tend to vanish with growing sample size, a common belief is that the methods are practically equivalent. To the contrary, we show on several experiments with various sample sizes that in some examples, the differences may be very likely. For a discrete distribution, exact estimates of differences between expected values of sample quartiles, given by two different methods, are derived. This implies that it is crucial that in any application, the choice of the method for computation of quartiles (or, percentiles) is explicitly given.

Keywords: quantiles, percentiles, sample quartiles.

Pages: 379 – 388 | Full PDF Paper