Level of Confidence >Level of Confidence Confidence in which the interval will contain the unknown population parameter >A percentage(less than 100%),is usually symbolized by(1-a)X100%,where a is the proportion in the tails of the distribution that is outside the confidence interval. Statistics for Ma nagers Using Microsoft Excel Chap 7-11Statistics for Managers Using Microsoft Excel Chap 7-11 Level of Confidence Level of Confidence Confidence in which the interval will contain the unknown population parameter A percentage (less than 100%), is usually symbolized by (1- )X100%, where  is the proportion in the tails of the distribution that is outside the confidence interval