Chi-Squared Distribution and the Central Limit Theorem

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This Demonstration explores the chi-squared distribution for large degrees of freedom , which, when suitably standardized, approaches a standard normal distribution as
by the central limit theorem. In this Demonstration,
can be varied between 1 and 2000 and either the PDF or CDF of the chi-squared and standard normal distribution can be viewed. You can also see the difference between the two distributions, which becomes useful for large
.
Contributed by: Peter Falloon (March 2011)
Open content licensed under CC BY-NC-SA
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Details
If are independent standard normal variables, then the random variable
follows the chi-squared distribution with mean
and standard deviation
. Taking the standardized variable
, the central limit theorem implies that the distribution of
tends to the standard normal distribution as
.
It can be seen that the chi-squared distribution is skewed, with a longer tail to the right. However, the PDF has maximum value at (for
), which is equivalent to
, so the skew disappears in the limit as
.
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