Help. Have answer but teacher says wrong.

[Oasis]

A study of 500 pastors in the Baptist Church found that their sermons lasted an average of 20 minutes with a standard deviation of 3 minutes. If a sample of 50 pastors is selected, what is the probability that their sermons will average more than 21 minutes?

21-20
3/√50
=2.36

Z> 2.36 = .0091

My teacher said the z score is correct but the probability is not .0091 but .86 and I don't understand what I'm doing wrong.

Please help.

[jahred]

your instructor is wrong, it's .0091.

[jamesmartinn]

I can also confirm your instructor is wrong, I just checked the normal table in my text and you're dead on.

[TheEcologist]

A study of 500 pastors in the Baptist Church found that their sermons lasted an average of 20 minutes with a standard deviation of 3 minutes. If a sample of 50 pastors is selected, what is the probability that their sermons will average more than 21 minutes?

21-20
3/√50
=2.36

Z> 2.36 = .0091

My teacher said the z score is correct but the probability is not .0091 but .86 and I don't understand what I'm doing wrong.

Please help.

I can confirm that with one glance at the z-score. You're right, your teacher is wrong

[Oasis]

Thanks. .............