The confidence region appears symmetric around the mean. This indicates they are using the normal approximation.
Exact confidence regions can be found, if you do it using Binomial instead.
The question to be asked, if m out of n is the frequency, is for which values of p do you have P(m>=M) = 0.975 and for which value of p do you have P(m<=M) = 0.975, where M ~ Binimial(n,p).
Exact confidence regions can be found, if you do it using Binomial instead.
The question to be asked, if m out of n is the frequency, is for which values of p do you have P(m>=M) = 0.975 and for which value of p do you have P(m<=M) = 0.975, where M ~ Binimial(n,p).
It can be solved easily too.