Correlation for 2 sets of continuous
values: Pearson Product-moment Coefficient (*r*)

interval
scale -
possesses equal intervals, along with ordinal scale qualities
(order, direction). See Scaling module, Levels of measurement. |

Use the Pearson coefficientwhen **both** variables
are at the interval level
of measurement and normally-distributed in the population. It
can be calculated in Excel if you have the data analysis module installed.

Example: A researcher wants to know whether scores on a linguistic ability test predict scores on the final exam in an Arabic language class. Here are the data from a dozen participants:

SubjectLinguistic aptitude (X)Final exam score (Y)1 5

5

2 10

20

3 6

4

4 8

15

5 4

11

6 4

9

7 3

12

8 10

18

9 2

7

10 6

2

11 7

14

12 9

17

Take a look at the formula - just to get the idea (and in case you ever need it). You don't need to memorize it.

Here is the statistical result for the above language data:

Hand calculation example.

Next section: Correlation
for ranks, Spearman *rs*