1. Lesson 12.1 Stem-and-Leaf Plots
Essential Question: How do you make and interpret stem-and-leaf plots?

2. Before we start…
Group the prices according to the tens digit and complete the table.
The data below shows the prices of 14 brands of jeans. Write the data in numerical order.
25, 35, 29, 18, 20, 40, 26, 28, 33, 30, 39, 42, 38, 26
Tens Digit
Data 1 2 3 4

3. What is a stem-and-leaf plot?
A data display that organizes data based on their digits.
stem (the leading digit(s)) and a leaf (the last digit)
A key that tells you how to read the data.

4. How do you make a stem-and-leaf plot?
Separate the data into stem and leaves.
List the stems in numerical order.
Write the leaves in increasing order. Include a key to show what the stems and leaves represent.

5. Track Hurdlers entering the 200 meter hurdles at a track meet were ranked according to their qualifying times, in seconds, shown below.

6. Speeds of Animals The table lists the maximum running speeds of various animals. Display the speeds of the animals shown in a stem-and-leaf plot.
Animal
Speed (mi/h)
Elk 45
Cheetah 70
Greyhound 39
Wildebeest 50
Quarter horse 47
Zebra 40
Giraffe 32
Coyote 43

7. Baseball The number of homeruns hit by the 20 baseball players with the best single season batting averages in Major League Baseball since 1900 are listed below. Make a stem-and-leaf plot of the data.
14, 25, 8, 8, 7, 7, 19, 37, 39, 18, 42, 23, 4, 32, 14, 21, 3, 12, 19, 41

8. Video Games The prices of video games are listed below
Video Games The prices of video games are listed below. Make stem-and-leaf plot of the prices.
$40, $15, $10, $19, $12, $24, $15, $39, $51, $50, $35, $20, $47, $36, $30, $25, $27, $29, $24, $43, $29

9. How do you interpret stem-and-leaf plots?
Read the key carefully so you understand the data in a stem-and-leaf plot.

10. The stem-and-leaf plot shows the number of video games sold at a store each day over two weeks. Find the mean, median, mode and range of the data.

11. The stem-and-leaf plot shows the ages of people at a reunion
The stem-and-leaf plot shows the ages of people at a reunion. How many people attended the reunion? How old was the oldest person there?

12. What is a double stem-and-leaf plot?
It’s a stem-and-leaf plot with two sets of stems.
It’s used to compare two sets of data.

13. Gymnastics The back-to-back stem-and-leaf plot shows the ages of members of the U.S. men’s and women’s 2004 Olympic gymnastics teams. Compare the ages of the gymnasts on the two teams.

14. Test Scores The double stem-and-leaf plot shows the test scores for Beth’s class and Marissa’s class. Overall which class had better test scores?

15. How do you make and interpret stem-and-leaf plots?

16. Ticket Out the Door
The stem-and-leaf plot shows the body lengths in feet of eight mountain lions. What is the length of the longest mountain lion?