Detecting skewness and kurtosis by letter values: a new proposal

Abstract

In this paper some new indices of sample shape ( skewness and kurtosis) are defined by means of letter values (Turkey, 1977). The letter index of skewness (l.c.s.) is built by fitting the standardized sample midsummaries with a least squares straight line, while the letter index of kurtosis (l.c.k.) is obtained by fitting the pseudosigmas (after a simple transformation), in the same way. A robust modification of the above defined indices is proposed. Finally, an application to a set of geographical data is given, with some comments about the effect of outliers.