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cyclonefb3
04-08-2008, 10:10 PM
An actor claims he signs 90% of autographs asked for. A sample of 100 fans is taken with a normal distribution. What is the probability that the actor will give more than 90% of them autographs.

mean = 60
SD = 30
n=100

So I did this:

z = estimate - hypothesis 90 - 0
-------------------- --------- = 3
SD of estimate 30


z = 3

When you look on a normal table the z value at 3 = .9987

Does that mean there is 99% probability of this happening or am I doing this wrong?

tkhunny
04-09-2008, 11:00 AM
You have the wrong side. It appears you have calculated the probability of LESS than 90%.