Pearson's r

This section introduces Pearson's correlation and explains what the typical values represent. It then elaborates on the properties of r, particularly that it is invariant under linear transformation. Finally, it introduces several formulas we can use to compute Pearson's correlation.

Computing Pearson's r

Questions

Question 1 out of 4.

What is the correlation between the two variables $\mathrm{X}$ and $\mathrm{Y}$ listed below? (We suggest you use a stat program or Analysis Lab).

_________

X Y

8 10

10 9

10 11

11 11

12 8

12 10

15 14

5 8

11 11

9 9

11 12

10 13

7 12

8 7

6 9

15 12

9 10

10 11

9 11

7 5

8 7

8 10

8 6

6 9

10 9

Question 2 out of 4.

What deviation score on $\mathrm{X}$ corresponds to the raw score of $\mathrm{6}$ ?

_________

X Y

2 4

4 3

6 5

Question 3 out of 4.

What is the sum of $\mathrm{xy}$ ?

_________

X Y

2 4

4 3

6 5

Question 4 out of 4.

What is the effect on the correlation of adding $\mathrm{12}$ to every score on one variable?

The correlation may go up or down, it depends on the data.
The correlation will increase.
The correlation will not change.