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From "Brent Worden" <>
Subject Re: [math] Questions regarding probability distributions
Date Wed, 13 Oct 2004 21:08:00 GMT
Here's my basis for the exponential, chi-squared, and gamma distribution design (forgive me
for reiterating some points made by others):

Exponential is separate because both the CDF and inverse CDF have closed form computations.
 This provides better performance and higher accuracy than the iterative method approximation.

Both exponential and chi-squared are separate from gamma to provide access only to the parameters
specific to each distribution.

In chi-squared case, extension could have easily been use but this would have exposed the
alpha and beta properties in chi-squared.  This would allow users to modify the properties
in an uncontrolled fashion, possibly resulting in a disfunctional distribution.  Thus, encapsulation
was used to hide the gamma properties and only expose the relavent chi-squared properties.

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