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.