28. baby talk: in a sample of 77 children, the mean age at which they
first began to combine words was 16.51 months, with a standard
deviation of 9.59 months.
a. construct a 95% confidence interval for the mean age at which
children first begin to combine words.
b. if a sample of 50 children had been studied, would you expect
the confidence interval to be wider or narrower than the interval
constructed in part (a)? explain.