posted by melinda .
The average length of an adult blue whate is 30 meters with a standard deviation of 5.7 meters. If a sample of 31 whales is taken, what is the probability that their average lenght differs from the mean by more than 2.0 meters
Use z-scores using sample size:
z = (x - mean)/(sd/√n)
Find two scores:
z = (32 - 30)/(5.7/√31)
z = (28 - 30)/(5.7/√31)
Find the probability between the two z-scores using a z-table. Subtract that value from 1 for your answer.
I hope this will help get you started.