Author: Kathy Halverson
Last saved by: Glencoe Mathematics
Company: Halverson Household

Lesson 12-1

Example 1	Draw a Stem-and-Leaf Plot
SPEEDS	The data below are speeds (in miles per hour) of cars on a stretch of local highway. Display the data in a stem-and-leaf plot.

	65    70    54    80    72    63    59    63    69    72   75    65    67

Step 1	Find the least and greatest number. Then identify the greatest place value digit in each number.  In this case, tens.

54	
The greatest number has 8 in the tens place.

The least number has 
5 in the tens place.

80

Stem |

5
6
7
8

Step 2	Draw a vertical line and write the stems from 5 to 8 to the left of the line.

Stem | Leaf

5
6
7
8

4 9
5 3 3 9 5 7
0 2 2 5
0

Step 3	Write the leaves to the right of the line, with the corresponding stem. For example, for 63, write 3 to the right of 6.

Stem | Leaf

5
6
7
8

4 9
3 3 5 5 7 9
0 2 2 5
0

	6 | 3 = 63 mph

Step 4	Rearrange the leaves so they are ordered from least to greatest. Then include a key or an explanation.

Example 2	Interpret Data
CLASS ATTENDANCE	The stem-and-leaf plot lists the daily attendance in a 
junior high math class.

Stem | Leaf

1
2
3

4 4 6 9
2 3 7 7 8 9 9
0 2 2 4

| 29 = 29 students

a.	In which interval do most of the attendance totals occur?
Most of the data occurs in the 20-29 interval.

b.	What is the difference between the lowest attendance total and the highest attendance total?
The lowest attendance total is 14 and the highest is 34. The difference is 34 – 14 
or 20.

c.	What is the median attendance total?
The median, or the number in the middle, is 27.

Example 3	Compare Two Sets of Data
WEATHER	The average monthly temperatures for Cleveland, Ohio and Miami, Florida are shown.

Cleveland, OH | | Miami, FL

9 5
8 8 6 4 2
9 7 3
7 6 2 2
9 5 3 3 1
8 8 4 4 2
7 5 5 3
1

1
2
3
4
5
6
7
8

8
0 3 6 6 9
4 7 7 8 9 9
2 6 6 7 7 8 9
0 2 3 3 5 7 8

24 = 42 | | | 56 = 56

a.	Which city has lower monthly temperatures?
Cleveland experiences temperatures in the 10’s, 20’s, and 30’s. So, it has lower monthly temperatures.

b.	Which city has more varied temperatures?  Explain.
The data for Cleveland are spread out, while the data for Miami are clustered.  So, Cleveland has the more varied temperatures.