Question

A random variable X follows a Binomial distribution; i.E. X ~ B(12, p) with a variance of 1.92. Compute the possible values of p

Answer 1

2 Answers:   p = 0.2 and p = 0.8

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Explanation:

Any binomial distribution has two unique components to it: The number of trials n, and the probability of success p.

We're given n = 12, and we need to find p.

The variance of a binomial probability distribution is given by the formula n*p*(1-p). Plug in n = 12 and set this equal to 1.92

So the equation to solve is 12p*(1-p) = 1.92

Solve for p using a graphing calculator or you could apply the quadratic formula. Either way, you should get the two results of p = 0.2 and p = 0.8

Note that if p = 0.2, then 1-p = 1-0.2 = 0.8, and things flip around when p = 0.8.