The formula for the population proportion is:
n = p ± Zc
where p = confidence level = 0.2
n = proportion = 0.22
= standard error = 0.01
Finding for Zc:
.20+(.01)=.22
Zc = 2
Referring to Critical value table for standard normal curve, a Zc value of 2 is equivalent to 95% Confidence Level.
Answer: 95% Confidence Level