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.
edit: I realise this is essentially a homework question so I've added the tag.