Question: how to calculate 95 upper confidence level?
Answer: The formula for the 95% confidence interval using the normal approximation is p ±1.96√[p(1-p)/n], where p is the proportion and n is the sample size. Thus, for P=0.20 and n=100, the confidence interval would be ±1.96√[0.20(1-0.20)/100], or 0.20±0.078.