Page 122 - DECO504_STATISTICAL_METHODS_IN_ECONOMICS_ENGLISH

Statistical Methods in Economics Pavitar Parkash Singh, Lovely Professional University

Notes Unit 8: Skewness and Kurtosis:

Karl Pearson, Bowley, Kelly's Methods

CONTENTS
Objectives
Introduction
8.1 Meaning, Definition and Types of Skewness
8.2 Karl Pearson, Bowley and Kelly’s Methods
8.3 Kurtosis

8.4 Summary
8.5 Key-Words
8.6 Review Questions
8.7 Further Readings

Objectives

After reading this unit students will be able to:
• Describe the Meaning, Definition and Types of Skewness.
• Know the Measures of Skewness.
• Explain Karl Pearson, Bowley and Kelly’s Methods.
• Understand Kurtosis.
Introduction

Measuring of central tendencies reveal the concentration of frequencies towards the central value of
the series and methods of dispersion reveal the dispersal of values in relation to the central value. But
the nature of dispersal of values on either sides of an average is not known by measuring dispersion.
Similarly, Kurtosis is yet another measure which tells us about the form of a distribution. Thus, it can
be said that the central tendencies and dispersion measures should be supplemented by measures of
skewness and kurtosis so that a more elaborate picture about the distribution given can be obtained.
The study becomes more important in subjects of economics, sociology and other social sciences
where normal distribution in a series usually does not occur. However, studies hold importance in
biological sciences and other physical sciences as well.
8.1 Meaning, Definition and Types of Skewness

Skewness—Meaning and Definition

The word ‘skewness’ is the opposite of symmetry and its presence tells us that a particular distribution
is not symmetrical or in other words it is skewed. The word ‘skewness’ can be understood by the
following definitions given by eminent statisticians, economists and mathematicians.
(1) As per Croxten and Cowden, “When a series is not symmetrical it is skewed.”
(2) In the words of Simpson and Kafka, “Measures of skewness tell us the direction and the extent of
skewness. In symmetrical distribution the arithmetic mean, median and mode are identicle.
The more the mean moves away from mode, the larger the asymmetry or skewness.”

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