A real estate company is interested in testing whether, on average,
families in Gotham have been living in their current homes for less time
than families in Metropolis have. Assume that the two population variances
are equal. A random sample of 100 families from Gotham and a random sample
of 150 families in Metropolis yield the following data on length of
residence in current homes.
what is the estimated standard error of the
difference between the 2 sample means?