How to Use Excel's BetaDist Function

By eHow Computers Editor

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Excel's BetaDist function calculates the cumulative beta probability density function. This function is used to measure the variation of a fraction of something across samples such as the amount of time people watch television each day. The following steps will show how to use Excel's BetaDist function.

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Instructions

Difficulty: Moderate

Step1

Learn the syntax of BetaDist. It is BetaDist (x,alpha,beta,A,B) where x is the value at which to evaluate the function, alpha is the alpha parameter of the beta distribution and beta is the beta parameter of the beta distribution. Parameters A and B are optional and will be explained in Step 2.

Step2

Include A as the lower bound to x and B as the upper bound to x when a non-standard cumulative beta distribution is desired. Otherwise, BetaDist will use the standard cumulative beta distribution where A=0 and B=1.

Step3

Study the way BetaDist works. BetaDist returns the fraction given by Bx(a,b)/B(a,b) where Bx(a,b) is the incomplete beta function and B(a,b) is the regularized incomplete beta function.

Step4

Observe the error conditions of BetaDist. BetaDist will return the #Value! error value if any argument is non-numeric. BetaDist will return the #Num! error value if alpha <= 0 or beta <= 0.

Step5

Look at an example of BetaDist.

=BetaDist(2,8,10,1,3) returns 0.685470581.

0.685470581 is the value at which to evaluate the beta distribution.
8 is the alpha parameter of the beta distribution.
10 is the beta parameter of the beta distribution.
1 is the lower bound of x.
3 is the upper bound of x.