1. Lesson 12.2 Box-and-Whisker Plots
Essential Question: How do you make and interpret box-and-whisker plots?

2. Before we start…
What is the median? What is the least score? What is the highest score? What is the median of the first half of data? What is the median of the second half of data?
Patrick played 11 rounds of golf on a golf course. His scores are shown below.
75, 78, 71, 70, 72, 76, 73, 81, 79, 75, 72

3. What is a box-and-whisker plot?
It organizes data values into four groups.
lower and upper halves
lower quartile = median of lower half
upper quartile = median of upper half

4. How is the data divided?
The ordered data is divided into four parts using: - the median - the upper quartile - the lower quartile

5. What is the lower quartile?
The median of the lower half of the data
What is the upper quartile?
The median of the upper half of the data

6. What is the lower extreme?
The least data value in a set
What is the upper extreme?
The greatest data value in a set

7. How do you make a box-and-whisker plot?
Order the data.
Find the median and the quartiles.
Plot the median, the quartiles, and the extremes below a number line.
Draw a box connecting the quartiles.
Draw a vertical line through the median.
Draw “whiskers” from the box to both extremes.

8. Bridges The lengths, in meters, of the world’s ten longest suspension bridges are listed below. Make a box-and-whisker plot of the bridge lengths.

9. Roller Coasters The heights, in feet, of 10 suspended roller coasters in the United States are 35, 42, 42.5, 60, 60, 70, 76, 78, 81, and 100. make a box-and-whisker plot of the data.

10. Exercise Fran recorded how many minutes she walked each day
Exercise Fran recorded how many minutes she walked each day. Make a box-and-whisker plot of the data.
25, 45, 48, 48, 52, 52, 55, 57, 65, 75

11. DVD Rentals The number of DVDs rented each day over two weeks is shown
DVD Rentals The number of DVDs rented each day over two weeks is shown. Make a box-and-whisker plot of the data.
38, 42, 50, 65, 82, 91, 88, 40, 34, 41, 71, 93, 87, 94

12. How do you interpret box-and-whisker plots?
4 parts:
2 parts of the box
50% of data
2 parts of whiskers
Each part contains approximately 25% of the data

13. Watches The prices of the watches at a store are summarized in the box-and-whisker plot below.
Suppose all of the watches under $31 are on clearance. About what fraction of the watches are on clearance?
Suppose all of the watches from $31 to $71 are on sale. About what fraction of the watches are on sale?

14. Football The box-and-whisker plots represent the number of points scored in each game of the season for the New England Patriots and the St. Louis Rams. What conclusions can you make about the data?

15. Food Science You are testing whether a fertilizer helps tomato plants grow. You divide the plants into two equal groups, and give fertilizer to plants in Group 2, but not to Group 1. The box-and-whisker plots show how much the plants grew, in centimeters, for each group of plants after two weeks.
About what fraction of the unfertilized plants grew as much as any of the fertilized plants?
About what fraction of the fertilized plants grew 4 to 8 centimeters?

17. What is the interquartile range?
Is the difference of the upper quartile and the lower quartile
It’s a measure of the spread of the data

18. What is the upper extreme. What is the lower quartile
What is the upper extreme? What is the lower quartile? What is the range? What is the median? What is the upper quartile? What is the interquartile range?

19. How do you make and interpret box-and-whisker plots?

20. Ticket Out the Door
The box-and-whisker plot shows the heights, in feet, of waves at a beach during one day. What is the lower quartile?