Question

Assume that a sample is used to estimate a population proportion p. Find the 90% confidence interval for a sample of size 279 with 38% successes. Enter your answer as an open - interval (i.e., parenthesis) using decimals (not percents) accurate to three decimal places.

Confidence Interval = ______________.

Answer 1

n = 279

$\hat{p}$ = 0.38

$\alpha$ = 0.10

From Table, criticalvalues of Z = $\pm$ 1.645

Confidence Interval:

0.38 +1.645 x 0.38 x (1 – 0.38) 279 = (0.332, 0.428)

So,

Answer is:

(0.332, 0.428)