Respuesta :
Answer:
The 99% confidence interval for the true percentage of smokers of all people who completed 4 years of college is closest to (0.1475, 0.2185).
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of [tex]\pi[/tex], and a confidence interval [tex]1-\alpha[/tex], we have the following confidence interval of proportions.
[tex]\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]
In which
Z is the zscore that has a pvalue of [tex]1 - \frac{\alpha}{2}[/tex].
For this problem, we have that:
There are 785 students, so [tex]n = 785[/tex]
18.3% of them smoke, so [tex]p = 0.183[/tex].
99% confidence interval
So [tex]\alpha = 0.01[/tex], z is the value of Z that has a pvalue of [tex]1 - \frac{0.01}{2} = 0.995[/tex], so [tex]Z = 2.575[/tex].
The lower limit of this interval is:
[tex]\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.183 - 2.575\sqrt{\frac{0.183*0.817}{785}} = 0.1475[/tex]
The upper limit of this interval is:
[tex]\pi + z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.183 + 2.575\sqrt{\frac{0.183*0.817}{785}}{119}} = 0.2185[/tex]
The 99% confidence interval for the true percentage of smokers of all people who completed 4 years of college is closest to (0.1475, 0.2185).
