# Math Help - Binomial Distribution Help

1. ## Binomial Distribution Help

Hey everyone,
I somewhat know how to do this question but I can't seem to get the answer..

Let x be a binomial random variable and suppose n= 20, p=0.4. Then P(μ-σ ≤ x ≤ μ+σ) is:
I know that μ = np = 8
I know that σ is sqrt(npq) = 2.19

Therefore, μ-σ = 5.81 and μ+σ = 10.18 so the area covered by 1 standard deviation is 4.38

So to find P(area covered by 1 standard deviation) I would use the z-score: z = x-μ/σ

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This is where i get stuck lol. any help? I know I'm almost there (i think)

2. ## Re: Binomial Distribution Help

nevermind, I figured this out.