試題詳解

7.A consumer protection agency is com paring he work of two electrical contractors. The agency plans to inspect residences in which each of these contractors has done the wiring in order to estimate the d ifference in the proportions of residences that are electrically deficient. Suppose the proportions of residences with deficient work are expected to be about . 2 for both contractors. How many homes should be sampled in order to estimate the difference in proportions using a 90% confidence interval of width . 5? )”
(A)
(B)
(C)
(D)