A survey of a group of seventh graders and a group of teachers at a local middle school asked how many siblings they each have. The dot plots below show the results. Students A dot plot titled Students. A number line going from 0 to 9 labeled number of siblings. There are 2 dots above 0, 4 above 1, 7 above 2, 5 above 3, 2 above 4, and 0 above 5, 6, 7, 8, and 9. Teachers A dot plot titled Teachers. A number line going from 0 to 9 labeled Number of siblings. There is 1 dot above 0, 3 dots above 1, 2 above 2, 4 above 3, 5 above 4, 3 above 5, 1 above 6, 0 above 7, 1 above 8, and 0 above 9. What is closest to the difference between the means of the two dot plots? 0.5 1.0 1.5 2.0

Note that number of students here are the once that had at least one sibling, others without siblings are not used in the calculation, hence 5 students (student-0 to student-4) make up total number of students, while the remaining 4 students (student-4 to student-9) are disregarded.

Therefore, mean = 20 ÷ 5 = 4 siblings.

Teachers No. of Siblings

student 0 1

student 1 3

student 2 2

student 3 4

student 4 5

student 5 3

student 6 1

student 8 1

Total 20

mean = (total number of siblings) ÷ (total number of students)

note that 8 students are used for the calculation, same reason as explained above

mean = 20 ÷ 8 = 2.5

Mean difference between the two plots = 4 - 2.5 = 1.5.