Can a reported mean of your article data be treated as a value from a population having a normal distribution? Why or why not? As stated in our book "The normality method for finding a confidence interval estimate of u is robust against a departure from normality which means that the normality requirement is loose. The distribution need not be perfectly bell-shaped but should appear to be somewhat symmetric with one mode and no outliers"[ CITATION Tri18 \\1 1033 ]. The two confidence levels, which we anticipate would fit the mentioned misconception: confidence level is the probability, 90% in this situation, that the population mean is contained in the built interval, being identical for both intervals. Naturally we see that the confidence intervals calculated do not overlap. The sample size n > 30 is a common guideline, but sample sizes of 15 to 30 are adequate if the population appears to have a distribution that is not far from being normal and there are no outliers. Because of this result, the consideration of the interval and its complement in the real number line, to our knowledge of probability, as a number between 0 and 1, and of complementary probability, we recognize the conflict in the interpretations of the confidence level applied to both intervals