Distribution and probabilty - parent and sample

Rba_Mandy

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Mar 19, 2009
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Ok I am completely lost, can anyone help me out? I have done the first question, and the second one is based on it.

The first question said:
The parent distribution of x is normal with mean 80 and standard deviation 9.
Based on samples of size n=25, find the mean and standard error of the sampling distribution of mean(sample).

I said: mean(pop) of mean(samp) = 80 (looked something like Mx = 80)
Standard devitaion(pop) of mean(samp) = 9/15 (looked like Ox = 9/5)

The second question is where I am lost.

It says find:
A. P(62 < x < 80)
B. P(71 < mean(samp) < 77)
C. x' such that P(mean(samp) > x') = .05

PS. Sorry for the confusing text, I don't know how to enter it w/ symbols. I did my best.
 
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