Holt CA Course 1

11-4 Scatter Plots

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Holt CA Course 1

11-4 Scatter Plots

Warm Up

Graph each point on the same coordinate plane.

1. A (5, 20)

2. B (20, 15)

3. C (10, 40)

4. D (30, 35)A

B

CD

Holt CA Course 1

11-4 Scatter Plots

SDAP1.2 Represent two numerical variables on a scatterplot and informally describe how the data points are distributed and any apparent relationship that exists between the two variables (e.g., between time spent on homework and grade level).

California Standards

Holt CA Course 1

11-4 Scatter Plots

Vocabulary

scatter plotcorrelationpositive correlationnegative correlationno correlationline of best fit

Holt CA Course 1

11-4 Scatter Plots

A scatter plot is a graph with points plotted to show a possible relationship between two sets of data.

Holt CA Course 1

11-4 Scatter Plots

Use the given data to make a scatter plot of the weight and height of each member of a basketball team.

Additional Example 1: Making a Scatter Plot of a Data Set

Use the table to make ordered pairs for the scatter plot.The points on the scatter plot are (71, 170), (68, 160), (70, 175), (73, 180), and (74, 190).

Holt CA Course 1

11-4 Scatter Plots

Use the given data to make a scatter plot of the weight and height of each member of a soccer team.

Check It Out! Example 1

12062

13568

17569

15667

12563

Weight (lbs)Height (in)200

190

180

170

160

150

140

130

120

60 61 62 63 64 65 66 67 68 69

The points on the scatter plot are (63, 125), (67, 156), (69, 175), (68, 135), and (62, 120). Height

Weig

ht

Use the table to make ordered pairs for the scatter plot.

Holt CA Course 1

11-4 Scatter Plots

A correlation describes a relationship between two data sets. The correlation can help you analyze trends and make predictions. There are three types of correlations between data.

Holt CA Course 1

11-4 Scatter Plots

Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.

Additional Example 2: Determining Relationships Between Two Sets of Data

The graph shows that as area increases, population increases.

The graph shows a positive correlation between the data sets.

Holt CA Course 1

11-4 Scatter Plots

Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.

Check It Out! Example 2

Tornado Frequency

0

200

400

600

800

1000

1200

1940 1960 1980 2000

Year

Nu

mb

er

of

To

rna

do

s

The graph shows that as the year increases, number of tornados increases.

The graph shows a positive correlation between the data sets.

Holt CA Course 1

11-4 Scatter Plots

A line of best fit, or trend line, is a straight line that approximates the relationship between the data on a scatter plot. You can also use a line of best fit when making predictions based on data.

Holt CA Course 1

11-4 Scatter Plots

Use the data to predict how much a worker will earn in tips in 10 hours.

Additional Example 3: Using a Scatter plot to Make Predictions

Draw a line that has about the same number of points above and below it. Your line may or may not go through the data points.

According to the graph, a worker will earn approximately $24 in tips in 10 hours.

Find the point on the line whose x-value is 10. The corresponding y-value is 24.

Holt CA Course 1

11-4 Scatter Plots

Use the data to predict how many circuit boards a worker will assemble in 10 hours.

Check It Out! Example 3

According to the graph, a worker will assemble approximately 10 circuit boards in 10 hours.

Hours Worked 4 8 6 9 11

Circuit Board Assemblies 2 7 5 8 12

141210 8 6 4 2

2 4 6 8 10 12 14Hours

Cir

cu

it B

oard

Assem

blies

Draw a line that has about the same number of points above and below it. Your line may or may not go through the data points.Find the point on the line whose x-value is 10. The corresponding y-value is 10.

Holt CA Course 1

11-4 Scatter PlotsLesson Quiz: Part I

1. Use the given data to make a scatter plot.

Grading Period 1 2 3 4

Number of A’s 5 6 8 10

0

1

2

3

4

5

6

7

8

9

10

11

0 1 2 3 4

Grading PeriodN

umbe

r of

A's

Holt CA Course 1

11-4 Scatter PlotsLesson Quiz: Part II

Identify the correlation that you would expect to see between each pair of data sets.

2. the minimum wage and the year

3. the amount of precipitation and the day of the week

4. the amount of germs on your hands and the number of times you wash your hands in a day

no correlation

positive correlation

negative correlation