- Correlation - measure of relationship between 2 variables
- Scatter plot
- Linear - straight line, Formula: Y = bX + a
- a = Y intercept
- b = slope
Direction
Positive
Negative
Magnitude (Strength) of Relationship
Perfect
Imperfect
Pearson's r - a measure of the extent to which paired scores occupy the same or opposite positions within their own distributions.
Using Z scores
Computational equation -
Variability of Y accounted for by X - Prediction of Y by X
- Deviation of observed Y score from mean of Y scores =
- Total variability of Y scores =
- Therefore: r =
r2 - coefficient of determination
r is appropriate when:
There are other variations of r for:
Effects on r
Range -
Extreme Scores -
Correlation and Causation