Age at diagnosis for each of 20 patients under treatment for meningitis was given in a research paper. Suppose the ages (in years) were as follows. 18 18 25 19 21 20 69 18 23 18 20 18 18 20 18 19 28 16 18 18 (a) Calculate the values of the sample mean and the standard deviation. (Round your standard deviation to three decimal places.) sample mean 22.1 yr standard deviation yr (b) Compute the upper quartile, the lower quartile, and the interquartile range. upper quartile yr lower quartile 18 yr interquartile range yr (c) Are there any mild or extreme outliers present in this data set? (Enter your answers as comma-separated lists. If there is no answer, enter NONE.) mild outliers 25.28 extreme outliers 69 (d) Construct the boxplot for this data set