Statistics: Informed Decisions Using Data (4th Edition)

Published by Pearson
ISBN 10: 0321757270
ISBN 13: 978-0-32175-727-2

Chapter 9 - Section 9.1 - Assess Your Understanding - Applying the Concepts - Page 438: 45c

Answer

Confidence interval: $0.903\lt p ̂\lt0.937$

Work Step by Step

$level~of~confidence=(1-α).100$% $95$% $=(1-α).100$% $0.95=1-α$ $α=0.05$ $z_{\frac{α}{2}}=z_{0.025}$ If the area of the standard normal curve to the right of $z_{0.025}$ is 0.025, then the area of the standard normal curve to the left of $z_{0.025}$ is $1−0.025=0.975$ According to Table V, the z-score which gives the closest value to 0.975 is 1.96. $Lower~bound=p ̂-z_{\frac{α}{2}}.\sqrt {\frac{p ̂(1-p ̂)}{n}}=0.920-1.96\sqrt {\frac{0.920(1-0.920)}{1001}}=0.903$ $Upper~bound=p ̂+z_{\frac{α}{2}}.\sqrt {\frac{p ̂(1-p ̂)}{n}}=0.920+1.96\sqrt {\frac{0.920(1-0.920)}{1001}}=0.937$
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