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# A normal population has a mean of 64 and a standard deviation of 13. You select a random sample of 9.?

Compute the probability that the sample mean is: (Round your z values to 2 decimal places and final answers to 4 decimal places):

(a) Greater than 66.

Probability:

(b) Less than 62.

Probability:

(c) Between 62 and 66.

Probability:

Update:

(I am able to find the z values, but I am getting lost when it comes to the rest of the calculations.)

### 2 Answers

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- Mike GLv 78 months ago
μ = 64 and σ = 13

n = 9 so √n = 3

x̅ = Sample mean

a) z(x̅=66) = (66-64)/(13/3)

= 0.4615

From the z-tables

P(z>0.4615) = 0.3228

b) z(x̅=62) = (62-64)/(13/3) = -0.4615

P(z<-0.4615) = 0.3228

c) P(-0.4615<z<0.4615) = 0.3544

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- STEPHENLv 78 months ago
Do your own homework. If you don't understand it talk to your teacher. Me doing it for you won't teach you anything.

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