For earthquakes with a magnitude 7.5 or greater on the
Richter scale, the time between successive earthquakes has a
mean of 425 days and a standard deviation of 378 days. Suppose that
you observe a sample of four times between successive earthquakes
that have a magnitude of 7.5 or greater on the Richter scale.
a. On average, what would you expect to be the mean of the
four times?
__ days
b. How much variation would you expect from your answer in
part (a)? (Hint: Use the three-standard-deviations
rule.)
The sample mean is expected to fall between __ and __ days