Draw a picture. Suppose that there are two binomial populations. For the first, the true proportion of successes is 0.4; for the second, it is 0.5. Consider taking independent samples from these populations, 50 from the first and 60 from the second.
(a) Find the mean and the standard deviation of the distribution of p^1 - p^2.
(b) This distribution is approximately Normal. Sketch this Normal distribution and mark the location of the mean.
(c) Find a value d for which the probability is 0.95 that the difference in sample proportions is within ±d. Mark these values on your sketch.