Find the margin of error in estimating a binomial proportion for p=0.5 and n=400.

a. 0.049

b. 0.069

c. 1.96

d. 0.0012

The margin of error (MOE) can be calculated by using the formula:

MOE = 1.96 sqrt [p (1 - p) / n]

So substituting the values:

MOE = 1.96 sqrt [0.5 (1 - 0.5) / 400]

MOE = 0.049

Therefore answer:

A. 0.049