- are "measures of association"
- a measurement of linear (straight line) relationship
measure of association
- a number that measures how related two variables are
- when two variables are related, this means that when one changes, the other changes
Pearson's product moment correlation
- the most common correlation
- referred to as "the correlation"
- it is used with quantitative (numerical) variables
- the symbol is r
- most common
- correlation lies between -1 and 1
- the measure of how close the points in the scatterplot are to the best fitting straight line
- it's negative when the line goes down, positive when the line goes up, and 0 when the line is flat
the best fitting straight line
square of correlation
- sometimes called "variance accounted for" or "shared variance"
- it is interpreted as the amount of variance in the y variable accounted for by the x variable
error in the prediction
regression and correlation
- yeild three important numbers:
- slope of best fitting line
- intercept of best fitting line