I'm doing a practice problem for my upcoming midterm and am stuck on a question.(adsbygoogle = window.adsbygoogle || []).push({});

3. The number of hurricanes that occur in the caribbean during hurricane season is a random variable, where the mean number of hurricanes occurring is 8, or E(X) = 8, with a standard deviation of 2.83.

(a) Find the probability, that in any given hurricane season, the number of hurricanes in the caribbean will be greater than 4 and less than 12.

So I figured this follows a binomial distribution. Given that, I noted that E(X)= np = 8, and that SD(X) = sqrt(Var(X)) = sqrt(np(1-p)) = 2.83. Knowing that information, I solved for p in 2.83 = sqrt(np(1-p)) and subbed in np = 8, and eventually got p = -.0011125. Which must be wrong.(?)

I don't even know if I'm on the right track, or am making some silly mistake.

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# Probability of something happening given the mean and the standard deviation.

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