AP Stats (math)
posted by Kyle on .
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?

zscore = (2520.5)/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