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A binomial count has p = 0.2 and a standard deviation of 4…

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Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A binomial count has $p = 0.2$ and a standard deviation of $4$ . Find the number of trials $n$ and the mean of the count.

Need a reminder? The key ideaShow

For $X \sim B(n, p)$ :

\displaystyle P(X = k) = \binom{n}{k}p^k(1 - p)^{n-k}, \qquad \mu = np, \qquad \sigma = \sqrt{np(1 - p)}.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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