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It is estimated that 60% of U.S. households subscribe to cable TV. You would like to verify this statement for your class in mass communications. If you want your estimate to be within 5 percentage points, with a 95% level of confidence, how many households should you sample

Sagot :

Using the z-distribution, as we are working with a proportion, it is found that you should sample 577 households.

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.

The margin of error is given by:

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

In this problem, we have a 95% confidence level, hence[tex]\alpha = 0.95[/tex], z is the value of Z that has a p-value of [tex]\frac{1+0.95}{2} = 0.975[/tex], so the critical value is z = 1.96.

In this problem, the estimate is of [tex]\pi = 0.6[/tex], and we want a margin of error of M = 0.05, hence we solve for n to find the sample size.

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

[tex]0.05 = 1.96\sqrt{\frac{0.6(0.4)}{n}}[/tex]

[tex]0.05\sqrt{n} = 1.96\sqrt{0.6(0.4)}[/tex]

[tex]\sqrt{n} = \frac{1.96\sqrt{0.6(0.4)}}{0.05}[/tex]

[tex](\sqrt{n})^2 = \left(\frac{1.96\sqrt{0.6(0.4)}}{0.05}\right)^2[/tex]

[tex]n = 576.24[/tex]

Rounding up, you should sample 577 households.

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

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