3) Independent random samples of n1 = 500 and n2 = 500 observations were selected from binomial populations 1 and 2, and x1 = 120 and x2 = 147 successes were observed.

a) What is the best point estimator for the difference (p1-p2) of the two binomial proportions?

(b) Find the approximate standard error for the statistic used in part (a).

c) What is the margin of error for this point estimate?