Question

Joe heard from a reliable source that only 22% of people actually sleep 8 hours or more per night. You do a survey and find 58 out of 148 sleep for 8 hours or longer. Build a 95% confidence interval. Round to the nearest hundredth.

Answer 1

Answer:

95% Confidence interval:  (31.32%,47.04%)

Step-by-step explanation:

We are given the following in the question:

Sample size, n = 148

Number of people who sleep for 8 hours or longer, x = 58

$\hat{p} = \dfrac{x}{n} = \dfrac{58}{148} = 0.3918$

95% Confidence interval:

$\hat{p}\pm z_{stat}\sqrt{\dfrac{\hat{p}(1-\hat{p})}{n}}$

$z_{critical}\text{ at}~\alpha_{0.05} = 1.96$

Putting the values, we get:

$0.3918\pm 1.96(\sqrt{\dfrac{0.3918(1-0.3918)}{148}})\\\\ = 0.3918\pm 0.0786\\\\=(0.3132,0.4704)=(31.32\%,47.04\%)$

(31.32%,47.04%)  is the required 95% confidence interval.