2. A correlation is a relationship between two variables. 
A correlation is a relationship between two variables.  In this section we care about linear correlations, which means relationships that can be approximated by linear functions.

3. Correlation Coefficient . Measures the strength of
Correlation Coefficient  Measures the strength of a linear relationship  Tells how close to being in a perfect line the points are.  Also tells whether the general trend is upward of downward.

5. The correlation coefficient is denoted by the letter r. •
The correlation coefficient is denoted by the letter r. • r is always between and 1 (inclusive) • In a perfect correlation r = 1 or r = -1 • If there is no correlation, r = 0.

7. Typically r = .5 is the dividing line between strong and weak correlations.

9. If there is a definite pattern, but that pattern isn’t a line, r = 0 (or is close to it).

10. To find “r” on a graphing calculator, first (1 time only) go press 2nd – 0 (CATALOG)

11. Scroll through the choices until you find “DiagnosticOn”
Scroll through the choices until you find “DiagnosticOn”. Press ENTER twice.

12. Once you have done this, the Linear Regression (feature (STAT – CALC – #4) we did before will calculate “r”.

13. Important … Correlation does not mean causation. 
Important … Correlation does not mean causation.  Just because there is a correlation between variables, it doesn’t mean one causes the other.