Unit 3Sections 9.1

What we will be able to do throughout this chapter…

Determine relationships between two or more variables

Determine strengths of relationships

Determine what types of relationships exist

Determine what kind of predictions can be made from the relationship

Section 9.1

Correlation –a relationship between two variables.

Data is represented in ordered pairs (x, y)

x is the independent (or explanatory) variable.

y is the dependent (or response) variable.

Section 9.1

Section 9.1

Types of Correlation

Section 9.1

Types of Correlation

Constructing a Scatter Plot

Section 9.1

Construct a scatter plot for the data obtained in a study of age and systolic blood pressure of six randomly selected subjects.

Subject Age (x) Pressure (y)

A 43 128

B 48 120

C 56 135

D 61 143

E 67 141

F 70 152

Constructing a Scatter Plot

Section 9.1

Construct a scatter plot for the data obtained in a study of the number of absences and the final grades of seven randomly selected students from a statistics class.

Subject # of Absences (x)

Final Grade (y)

A 6 82

B 2 86

C 15 43

D 9 74

E 12 58

F 5 90

G 8 78

Constructing a Scatter Plot

Section 9.1

Construct a scatter plot for the data obtained in a study on the number of hours that nine people exercise each week and the amount of milk (in ounces) each person consumes per week.

Subject Hours (x) Amount (y)

A 3 48

B 0 8

C 2 32

D 5 64

E 8 10

F 5 32

G 10 56

H 2 72

I 1 48

Relationships

Example 1 – shows a positive relationship since as a person’s age increases their blood pressure tends to increase also.

Example 2 – shows a negative relationship since as the number of absences increases the final grade decreases.

Example 3 – shows no relationship since no pattern is discernable.

Section 9.1

Enter the data for your independent variable (x) into L1.

Enter the data for your dependent variable (y) into L2.

Press 2nd then Y= to bring up your Stat Plot menu.

Hit Enter for Plot 1 Hit Enter to turn your Plot 1 on Make sure the scatter plot is selected, Xlist is L1,

and Ylist is L2. Press ZOOM then 9 to bring up the Stat View Your scatter plot should be in the window

Section 9.1

Constructing a Scatter Plot Using a TI

Scatter Plot – Using the TI

Section 9.1

A researcher conducts a study to determine whether there is a linear relationship between a person’s height (in inches) and pulse rate (in beats per minute). The data is shown in the table below. Display the data in a scatter plot and describe the correlation.

Height (x) Pulse Rate (y)

68 90

72 65

65 88

70 100

62 105

75 98

78 70

64 65

68 72

Homework: Pgs. 481-482 (1, 2, 9-18, 21a, 22a)

Read and take notes on Section 9.1 (pgs. 473-475)