6. Independent random samples were drawn from two normal populations assumed to have the approximately
the same standard deviation, resulting in the following summary statistics:
n1 = 25, s1 = 4.8, n2 = 16, s2 = 5.1
(a) Calculate a pooled estimate of the common standard deviation of the two populations.
(b) What is the margin of error for a 99% CI for the difference of the means?