Suppose we were not sure if our sample of 30 is normal In wh

Suppose we were not sure if our sample of 30 is normal. In which of the following circumstances would we NOT be safe using a T procedure?

A. The mean and median of the data are not exactly equal.

B. A histogram of the data is moderately skewed.

C. The sample standard deviation is large.

D. A boxplot of the data shows the presence of a large outlier.

E. Thirty is always large enough for the sample mean to be approximately normal.

Solution

If box plot has large or low outliers, then it will not safe to use T procedure because in that case we cannot assume that distribution is normal. So option D is correct.