Last stat prob, I promise! heh

Thanks

need some help :(

a. p(x>570)
z509 = 570-509/112 = .54

Quote:

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Originally Posted by Smokey007

Scores for men on the verbal portion of the SAT test are normally distributed with a mean of 509 and a standard deviation of 112.

a. If 1 man is randomly selected, find the probability that his SAT verbal score is more than 570.

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p(z>(570-509)/112) = p(z>0.545) = 1 - p(z<0.545) ~= 1-0.707 = 0.293

Quote:

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b. If 100 men are randomly selected, find the probability that their mean SAT verbal score is more than 570.

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The sample mean is normaly distributed with mean 509 and sd 112/sqrt(100)=11.2

So we want:

p(z>(570-509)/11.2) = p(z>5.45) ~= 0.

RonL