1. Box Plots March 20, 2015 7 th grade

2. What is a box plot? Box plots are used to represent data that is measured and divided into four equal parts. These equal parts are known as: Quartiles.

3. List Numbers in Order List numbers in order from Least to Greatest: Middle number is the median 21 22 24 26 31 35 35 41 43 47 51

4. Five Number Summary How the data is broken up: 21 22 24 26 31 35 35 41 43 47 51 Lower Half (before median) Upper Half (after median) Median 1 st Quartile (Q₁) Median of Lower Half 3 rd Quartile (Q₃) Median of Upper Half Minimum Maximum Five Number Summary – These will be used to create a Box Plot Minimum: 21 First Quartile (Q₁): 24 Median: 35 Third Quartile (Q₃): 43 Maximum: 51

5. Creating a Box Plot Using a number line and the five number summary, a box plot can be created to represent the data.

6. Creating a Box Plot (cont.) The data was: 21 22 24 26 31 35 35 41 43 47 51 With this specific data, it would be best to use intervals of 2 to represent the data on the number line, like this:

7. Creating a Box Plot (cont.) The data was: 21 22 24 26 31 35 35 41 43 47 51 To create a box plot: 1. Plot the “five number summary” over the number line using points for: - Minimum - 21 - 1 st interquartile (Q₁) - 24 - Median - 35 - 3 rd interquartile (Q₃) - 43 - Maximum – 51 2. Connect the 1 st interquartile, median, and 3 rd interquartile with boxes. 3. Connect the minimum and maximum to the boxes with “whiskers.” 4. Determine Range and Interquartile Range (IQR). - Range = Max – Min (51 – 21 = 30) - IQR = Q₃ - Q₁ (43 – 24 = 19) Min. Q₁ Median Q₃ Max.

8. Try Your Own Create box plots using the following data: 1)4, 7, 9, 13, 19, 21, 26, 29, 37 40 2) 81, 83, 86, 89, 91, 94, 95, 96, 98, 100, 102 3) 1, 8, 19, 29, 38, 48, 59, 70, 78

9. Homework After creating a box plot for each set, compare the Range and IQR for #3 to the Range and IQR for #1 and #2. Of the 3 problems, which has the greatest range? Which has the smallest range? Of the 3 problems, which has the greatest IQR? Which has the smallest IQR? What is the difference in the range for #1 and #2? What is the difference in the IQR for #2 and #3?