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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


Sagot :

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:

[tex]\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]

In which:

  • [tex]\pi[/tex] is the sample proportion.
  • z is the critical value.
  • n is the sample size.

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

The sample size and estimate are given by:

[tex]n = 2002, \pi = 0.71[/tex]

Hence, the lower bound is given by:

[tex]\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.71 - 2.575\sqrt{\frac{0.71(0.29)}{2002}} = 0.6839[/tex]

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

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

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