Posted by **Kyle** on Sunday, April 7, 2013 at 10:17am.

A large metropolitan area found that the time it takes for people to commute to work has a mean of 20.5 minutes and a standard deviation of 15.4 minutes. What is the probability that a random sample of 40 people have a mean commute time greater than 25 minutes?

- AP Stats (math) -
**Reiny**, Sunday, April 7, 2013 at 11:04am
z-score = (25-20.5)/15.4

then look up that z in your tables,

subtract that from 1

that is,

1 - value you looked up

or

you can use one of my favourite websites

http://davidmlane.com/normal.html

Make sure "area from value " is clicked on

enter the mean, the sd, and click on "below" and enter 25

The value of .6149 should agree with the value you found above

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