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In-s [12.5K]
2 years ago
12

We are studying the proportion of cities that have private garbage collector. We want a maximum error of 0.10 and a 95% confiden

ce level, and tentatively estimate the proportion at 0.50. What is the minimum number of cities we need to contact?
Mathematics
1 answer:
True [87]2 years ago
8 0

Answer:

The minimum number of cities we need to contact is 96.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of \pi, and a confidence interval 1-\alpha, we have the following confidence interval of proportions.

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

In which

Z is the zscore that has a pvalue of 1 - \frac{\alpha}{2}.

The margin of error is:

M = z\sqrt{\frac{\pi(1-\pi)}{n}}

95% confidence interval

So \alpha = 0.05, z is the value of Z that has a pvalue of 1 - \frac{0.05}{2} = 0.975, so Z = 1.96.

In this problem, we have that:

p = 0.5, M = 0.1

M = z\sqrt{\frac{\pi(1-\pi)}{n}}

0.1 = 1.96*\sqrt{\frac{0.5*0.5}{n}}

0.1\sqrt{n} = 0.98

\sqrt{n} = 9.8

(\sqrt{n})^{2} = (9.8)^{2}

n = 96

The minimum number of cities we need to contact is 96.

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