I have a sample with 1000 people which 382 agree, 578 disagree and 40 can't decide. I want to find the 99% confidence interval of the proportion of people who agree.
I know how how to discover using R the standard error, and then use it to find the 95% confidence interval. It's just make this calculation: (0.382-2SE,0.382+2SE).
My question is how to find the 99% confidence interval. Do I need R programming or I can do as a simple calculation?