Problem 12.1 The side-by-side box plot displayed in Figure 12.1 reveals an outlier in the group of students taught by method 3 (praised). (Outliers are discussed in Section 1.5.) Verify that 23 is the outlier by showing that it lies outside the interval (Q1 − 1.5 × IQR, Q3 + 1.5 × IQR), where IQR is the interquartile range and Q1, Q3 are the lower and upper quartiles of the arithmetic scores of the students taught by method 3.