3, No. 2
from Professor Cleary
If you were tempted to give the dermatology
response, wait till you hear two more terms: leptokurtic and platykurtic. These
describe two different distributions, all part of what is known as kurtosis, the
measure of the combined weight of the tails of a distribution in relation to the
rest of it. When tails become heavier, the kurtosis value increases; when they
are lighter, it decreases. A normal distribution has a kurtosis of 0, and is
called mesokurtic (A below). If a distribution is peaked (tall and skinny), its
kurtosis value is greater than 0 and it is said to be leptokurtic (No ointments
needed.) (B below). If, on the other hand, the kurtosis is flat, its value is
less than 0, or platykurtic (C below). The formula is as follows:
Note that some references to kurtosis do not subtract 3, as shown above.
SQCpack for Windows subtracts 3 in order to make the statistic 0 for a normal
Tip: Put your teenager in his place by protesting his leptokurtic behavior.
Copyright 2001 PQ Systems.
Please direct questions or problems regarding
this web site to the Webmaster.