Posted by kevin on Thursday, April 25, 2013 at 1:42pm.
The duration of time it takes General Motors to build a car is normally distributed with a mean of 31 hours and a standard deviation of 2 hours.
a) What is the probability that a single car, selected at random,
will take between 28 and 34 hours?
b) What is the probability that the mean of the times for a sample
of 25 cars will be between 28 and 34 hours?

statistics  PsyDAG, Friday, April 26, 2013 at 3:24pm
a) Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.
b) Z = (scoremean)/SEm
SEm = SD/√n
Use the table. 
statistics  Lisa, Tuesday, March 7, 2017 at 7:55pm
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