Dear all, I have a specification from a tool, which says, 80% of the reported measurements are within plus or minus 10% of the actual, at 95% confidence level. I am trying to make sense out of this statement. Assuming a normal distribution, please can someone tell me how to interpret these data? I was interpreting that 95% of the measurements will be within the shaded area represented by a normal curve. The right hand side limit will be = actual+10% of actual, the left side limit will be actual-10% of actual. Where does 80% come from? I am totally confused. Please help. Thanks.