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Measures of Dispersion, Skewness and Kurtosis

Authors
  • Rindskopf, D.
  • Shiyko, M.
Type
Book
Journal
International Encyclopedia of Education
Publication Date
Jan 01, 2010
Pages
267–273
Identifiers
DOI: 10.1016/B978-0-08-044894-7.01344-0
ISBN: 978-0-08-044894-7
Source
Elsevier
Keywords
License
Unknown

Abstract

In educational research, test scores are often summarized as if they emerge from a normal distribution. Such a distribution can be described by two parameters: the center (measured by the mean) and dispersion (measured by the variance or standard deviation). This article summarizes the most commonly used measures of dispersion: several types of range statistics, standard deviation, variance, and median absolute deviation. Their strengths and limitations are discussed. Two additional concepts – skewness and kurtosis – are discussed as a way to test normality of the distribution, as well as to describe departures from normality.

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