Advanced Math Advanced Math TopicsTopics

2.5 Stem-and-Leaf Plots and 2.5 Stem-and-Leaf Plots and Misleading GraphsMisleading Graphs

Graph paper and a ruler will help today!

The number of sales of condos in the Bay Area was recorded over theThe number of sales of condos in the Bay Area was recorded over the last 25 months. Create a stem-and leaf plot for the data.last 25 months. Create a stem-and leaf plot for the data.

3737 9595 3434 2626 4545

8888 8080 2424 6161 2828

4040 7878 6767 3232 7979

6767 2929 2828 2424 3535

6868 7272 9191 8686 7878

Steps1) Decide on how the stems and leaves will be identified(usually the leaf is the last digit& the stem is all other digits)

2) List all stems in a column in order from least to greatest

Stem Leaves

2

3

4

5

6

7

8

9

3) Place a leaf in each appropriatestem row (each leaf has the samewidth for uniformity-graph paper helps!)

7

8

0

7 8

5

0

8

9

2

4

4

7

8

1

6

1

2

2

6

5

8

9

5

8

4) Draw rectangles around each set of leaves.

Statistics are an important way to display information. As an educated person, it is vital that you understand the way the data is displayed before you make a conclusion, prediction, or decision based on the information. The followingexamples will illustrate:

Rainfall(in.)

Month

Jan Feb Mar Apr May

9.5

10.0

10.5

11.0

11.5

12.0 .. . . .

What are your initial thoughts?

Rainfall(in.)

Month

Jan Feb Mar Apr May

2

4

6

8

10

12 . . . ..

The two graphs display the same information!!

The truncated scale dramatically changes the look of the graph.

It is important to analyze a graph before making conclusions!!!

Assignment 2DAssignment 2D

P. 72 #1, #2 P. 77 #1-3P. 72 #1, #2 P. 77 #1-3