7a. The box-and-whisker plot would tell us that there are two extremes in the dataset. Because of this, using the mean as a measure of center won't be ideal since these extreme values would influence it. Therefore, the better measure of center for the data set is the median.
7b. The box-and-whisker plot shows us a representation of a wide range of student population. From that graph we can infer that the smallest student population is 10 and the highest one is 30 while the median sits at about 20 students.
7c. Since 23 falls exactly on the third quartile, we can say that 25% of the classrooms have 23 or more students. We have come up with this exact percentage based on the definition of the box-and-whisker plot as well as quartiles.
7d. 17 is the first quartile and therefore 25% of the classrooms have 17 or less students. Since we know before that 25% of the classrooms have 23 or more students, then we can accurately say that 50% of the classrooms have between 17 to 23 students.