Pediatric researchers carried out a study on various options for treating a child's cough. A sample of 120 children who were ill with an upper respiratory tract infection and their parents participated in the study. On the first day, a total symptoms score in points was measured for each child (higher indicating worse symptoms). That night 40 randomly selected children received dextromethorphan (DM, over-the-counter cough medicine), another 40 randomly selected children received a dosage of honey, and the remaining 40 were given no dosage at all. On the second day, the total symptoms score in points was measured again for each child and the improvement score was computed (improvement = day 1 score - day 2 score).

Box plots show to what extent the extreme values are from most of the data which consists of the five values given by the minimum value, the first quartile, the median, the third quartile, and the maximum value.

The smallest and largest data values label of the boxplot is given by the endpoints whereas the first quartile marks one end of the box and the third quartile marks the other end of the box. And the median falls inside the box which is denoted by a line through it.