Question

He normal pulse rate of a 13-year-old is between 70 and 100 beats per minute. As part of a health program, the medical staff at Grant Middle School measured the resting pulse rate of 12 randomly selected students in grades 7 and 8. The box plot shows the data for each group. Which statement correctly compares the data sets?
The difference of the medians is about half of the interquartile range of either data set.
The difference of the medians is about 2 times the interquartile range of either data set.
The difference of the medians is about one-fourth of the interquartile range of either data set.
The difference of the medians is about 4 times the interquartile range of either data set.

Answer 1

The difference of the medians is about half of the interquartile range of either data set.

Answer 2

From the box plot, it can be seen that for grade 7 students,
The least value is 72 and the highest value is 91. The lower and the upper quartiles are 78 and 88 respectively while the median is 84.

Thus, interquatile range of the resting pulse rate of grade 7 students is upper quatile - lower quartle = 88 - 78 = 10

Similarly, from the box plot, it can be seen that for grade 8 students,
The least value is 76 and the highest value is 97. The lower and the upper quartiles are 85 and 94 respectively while the median is 89.

Thus, interquatile range of the resting pulse rate of grade 8 students is upper quatile - lower quartle = 94 - 85 = 9

The difference of the medians of the resting pulse rate of grade 7 students and grade 8 students is 89 - 84 = 5

Therefore, the difference of the medians is about half of the interquartile range of either data set.