Abstract
A popular robust measure of dispersion of a random variable (rv) X is the median absolute deviation from the median med(|X - med(X)|), MAD for short, which is based on the median med(X) of X. By choosing Y = X, the MAD turns out to be a special case of the comedian med((X - med(X))(Y - med(Y))), which is a robust measure of covariance between rvs X and Y. We investigate the comedian in detail, in particular in the normal case, and establish strong consistency and asymptotic normality of empirical counterparts. This leads to a robust competitor of the coefficient of correlation as an asymptotic level-α-statistic for testing independence of X and Y. An example shows the weird fact that knowledge of the population med(X) does not necessarily pay (in the sense of asymptotic relative efficiency) when estimating the MAD.
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References
Box, G. E. P. and Muller, M. E. (1958). A note on the generation of random normal deviates, Ann. Math. Statist., 29, 610–611.
Epanechnikov, V. A. (1969). Nonparametric estimation of a multivariate probability density, Theory Probab. Appl., 14, 153–158.
Falk, M. (1986). On the estimation of the quantile density function, Statist. Probab. Lett., 4, 69–73.
Feller, W. (1970). An Introduction to Probability Theory and Its Applications, Vol. I. 3rd ed. (revised printing), Wiley, New York.
Feller, W. (1971). An Introduction to Probability Theory and Its Aplications, Vol. II, 2nd ed., Wiley, New York.
Hall, P. and Welsh, A. H. (1985). Limit theorems for the median deviation, Ann. Inst. Statist. Math., 37, 27–36.
Hampel, F. R. (1974). The influence curve and its role in robust estimation, J. Amer. Statist. Assoc., 69, 383–397.
Huber, P. J. (1981). Robust Statistics, Wiley, New York.
Pfanzagl, J. (1994). Parametric Statistical Theory, De Gruyter, Berlin.
Reiss, R.-D. (1989). Approximate Distributions of Order Statistics (With Applications to Nonparametric Statistics), Springer Series in Statistics, Springer, New York.
Rousseeuw, P. J. and Croux, C. (1993). Alternatives to the median absolute deviation, J. Amer. Statist. Assoc., 88, 1273–1283.
Rousseeuw, P. J. and Leroy, A. (1987). Robust Regression and Outlier Detection, Wiley, New York.
Rousseeuw, P. J. and Molenberghs, G. (1993). Transformation of non positive semidefinite correlation matrices, Comm. Statist. Theory Methods, 22, 965–984.
Serfling, R. (1980). Approximation Theorems of Mathematical Statistics, Wiley, New York.
Tukey, J. W. (1977). Exploratory Data Analysis, Addison-Wesley, Reading, Massachusetts.
Welsh, A. H. (1986). Bahadur representations for robust scale estimators based on regression residuals, Ann. Statist., 14, 1246–1251.
Xiang, X. (1994). A law of the logarithm for kernel quantile density estimators, Ann. Probab., 22, 1078–1091.
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Falk, M. On Mad and Comedians. Annals of the Institute of Statistical Mathematics 49, 615–644 (1997). https://doi.org/10.1023/A:1003258024248
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DOI: https://doi.org/10.1023/A:1003258024248