3. An experiment is required to estimate a process's process capability cp parameter to within ±20% of its true value with 95% confidence, i.e. a confidence interval for the population standard deviation of the following form is required: - P(ĉp(1 − 8) < cp < ĉp(1+8)) = 0.95 where cp will be determined from the sample data. Calculate the sample size for the experiment assuming that the distribution is normal.