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I have a math problem. I hardly know where to start. Can you help?

Here it is.  Wow..., this is really hard to read for  me.

How many close friends do you have? Suppose that the number of close friends adults claim to have varies from person to person with mean 9 and standard deviation 2.5. An opinion poll asks this question of an srs of 1100 adults. We will see in chapter 9 that in this situation the sample mean response x has approximately the normal distribution with mean 9 and standard deviation 0.075. What is P(8<=x-var<=10), the probability that the statistic x-var estimates the parameter mean to within +/- 1?


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1 Answer

P(8<=x-var<=10) ~ 1, since |(x-μ)|/σ > 13.

Attn: P(|(x-μ)|/σ = 3) = 99.7


Hi Robert:

While I appreciate the answer, can you explain it to me?