Example 1: page 161 #5

Example 2: page 160 #1

Explanatory Variable -

Response Variable -

independent variable

dependent variable

Correlation coefficient - r

Measures the strength and direction of the linear relationship between quantitative variables.

Strength

+ r = positive correlation

- r = negative correlation

1 1r

Direction .8r

.5 .8r

.5r

strong

moderate

weak

1

1i i

x y

x x y yrn s s

Recipe for r

There is a _(strength)___, ___(direction)____, linear relationship between __(explanatory)__ and __(response)__.

Let’s use the formula to find r. This will be the only time we do it by hand. After today we will find it using on the calculator.

Posted speed limit (mph) Ave. # of weekly reported accidents

55 28

50 25

45 21

40 17

30 11

25 6