Question

Are you getting enough sleep? Many kids aren’t getting enough sleep, and TV might be part of the problem. Among 2002 randomly selected 8- to 18-year-olds in the United States, 71% had a TV in their bedroom. What is the lower boundary of our confidence interval at the 99% level?
a. 6547
b. 6714
c. 6677
d. 6839

Answer 1

Using the z-distribution, it is found that the lower bound of the 99% confidence interval is given by:

d. 68.39%.

What is a confidence interval of proportions?

A confidence interval of proportions is given by:

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which:

• $\pi$ is the sample proportion.

• z is the critical value.

• n is the sample size.

In this problem, we have a 99% confidence level, hence$\alpha = 0.99$, z is the value of Z that has a p-value of $\frac{1+0.99}{2} = 0.995$, so the critical value is z = 2.575.

The sample size and estimate are given by:

$n = 2002, \pi = 0.71$

Hence, the lower bound is given by:

$\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.71 - 2.575\sqrt{\frac{0.71(0.29)}{2002}} = 0.6839$

Hence the lower bound is of 68.39%, which means that option D is correct.

More can be learned about the z-distribution at brainly.com/question/25890103

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