Spotlight: Word

Spotlight, November 26, 2014: Kurtosis

Image credit: whatilearned.wikia.com

Image credit: whatilearned.wikia.com

Kurtosis is a description of how sharply peaked a statistical distribution is and how far from the horizontal axis (how heavy) the tails are. The normal distribution has a kurtosis of 3 and moderately heavy tails and is called mesokurtic. Distributions that are pointier with heavier tails (farther above the horizontal axis) than the normal distribution are called leptokurtic, and those flatter than normal and with lighter tails are called platykurtic. Because of this relationship between the peakedness and the weight of the tails, leptokurtic distributions also have sides with greater curvature than the sides of mesokurtic and platykurtic distributions.

Sources: Weisstein, Eric W. “Kurtosis.” From MathWorld–A Wolfram Web Resource. http://mathworld.wolfram.com/Kurtosis.html (if you like math). Decarlo, Lawrence T. “On the Meaning and Use of Kurtosis.” Psychological Methods 2.3 (1997): 292-307. (if you like math drama)