You are studying the rate of incidence of skin cancer in people who live near the equator. Your survey of 200 people from the area has shown that 7 of them developed skin cancer.

Question

Provide a 99% confidence interval for the true rate of incidence.

Answer 1

Example of a proportional confidence interval formula:

CI99 = p + or - (2.58)[√(pq/n)]
...where p = x/n, q = 1 - p, and n = sample size.
Note: + or - 2.58 represents 99% confidence interval.

For p in your problem: 7/200 = .035
For q: 1 - p = 1 - .035 = .965
n = 200

I let you take it from here to calculate the interval.