How to Use Excel's BinomDist Function

By eHow Computers Editor

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Excel's BinomDist function returns the individual term binomial distribution probability. It is used to solve statistical problems where the number of tests is fixed and a test outcome is either a success or failure. The tests must be independent with a constant probability of success throughout the experiment. The following steps will show how to use Excel's BinomDist function.

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Instructions

Difficulty: Moderate

Step1

Learn the syntax of BinomDist. It is BinomDist (x,n,p,cumulative) where x represents the number of successes, n represents the number of trials, p represents the probability of success of each trial and cumulative represents a logical value to determine the form of the function.

Step2

Determine the probability that there will be x successes by setting cumulative to False. BinomDist will return the probability mass function as follows:

b(x;n,p) = n!(p^x(1-p)^(n-x))/(x!(n-x)!)

Step3

Calculate the probability there will be at most x successes by setting cumulative to True. BinomDist will return the cumulative distribution function as follows:

B(x;n,p)= sum of b(i;n,p) for each i from 0 to n inclusive.

Step4

Observe the way the arguments to BinomDist are evaluated: x and n are reduced to integers. BinomDist will return the #Value! error value if any of its arguments are non-numeric. BinomDist will return the #Num! error value if x < 0, x > n, p < 0 or p > 1.

Step5

Use BinomDist to figure the probability that six of the next 10 babies born are male.

=BinomDist (6,10,0.5,FALSE) returns 0.205078.

The number of successes (male babies) is 6.
The total number of tests (births) is 10.
The chances that a birth will be a boy is 0.5 (approximately).
Cumulative is False because we are calculating the probability for an exact number of successes.