Answer:
The 95% confidence the proportion of the population that does have at least one bilingual operator is (0.2359, 0.4307).
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 level of [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 z-score that has a p-value of [tex]1 - \frac{\alpha}{2}[/tex].
90 companies. 30 have at least one billingual operator.
This means that [tex]n = 90, \pi = \frac{30}{90} = 0.3333[/tex]
95% confidence level
So [tex]\alpha = 0.05[/tex], z is the value of Z that has a p-value of [tex]1 - \frac{0.05}{2} = 0.975[/tex], so [tex]Z = 1.96[/tex].
The lower limit of this interval is:
[tex]\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.3333 - 1.96\sqrt{\frac{0.3333*0.6667}{90}} = 0.2359[/tex]
The upper limit of this interval is:
[tex]\pi + z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.3333 + 1.96\sqrt{\frac{0.3333*0.6667}{90}} = 0.4307[/tex]
The 95% confidence the proportion of the population that does have at least one bilingual operator is (0.2359, 0.4307).
