Thread: Last stat prob, I promise! heh

Thanks

need some help

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

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.

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

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

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