I'm trying to understand confidence intervals but having some trouble. I've been doing some exercises I found online and I'm stuck on this question:
I have been given a 95% conﬁdence interval for a population proportion: (0.35, 0.40), a sample size of 200, and I need to find a 99% confidence interval. The methods I would go to first involve using standard deviation, which I don't have.
How can I approach this question without knowing variance? The whole quiz is about normal distributions, to give it some context.
This isn't really homework but I'm tagging it this way because I'm looking for a similar outcome. The quiz has answers at the end; what I want is to be able to solve it myself.