Regression Line I

Recap:

Mean is _______________________________________________________________

Median is _____________________________________________________________

Last class we drew a line that best fit the points on a scatter plot, which is called a ________________________. Today we will look at one method for finding the equation of the regression line, called the ___________________________.

the average. Add up all the values and divide by the number of values.

the middle number. If there are two middle numbers, add them and divide by 2.

regression linemedian-median line method

There are 6 steps to follow in this method:

1) List and order the distribution pairs (points) according to their ___________________. 2) Divide the ordered pairs into _____ equal groups. If this is not possible, divide them so the _____ and _____ groups have an equal number.

3)Calculate the __________ x-coordinate and y-coordinate in each of the three groups in order to form the ___________ pairs

4) Find the mean of the x-coordinates and y-coordinates of . These will be the coordinate for _____________.

5) Calculate the slope of the line passing through points ____ and ____.

6) Find the equation of the line that passes through ___________ and has the same slope as the line that passes through ________________.(*Hint* Use the point-slope method from Unit 1)

x-coordinates

31 3

medianmedian

point P

M1 M3

point PM1 and M3

0x

y

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

18

16

14

12

10

8

6

4

2

1) List the points by their x-coordinates 2)Divide the points into 3 equal groups.

3) Calculate the median x-coordinate and y-coordinate for each group to make points M1, M2, and M3.

4) Find the mean of the x- and y-coordinates of points M1, M2, and M3 to make point P.

5) Calculate the slope of the line that goes through M1 and M3.

6) Find the equation of that line with point P and same slope as M1 and M3.(*Hint* Use the point-slope method)

Now you try one! Do question one from the homework sheet

1) List the points by their x-coordinates 2)Divide the points into 3 equal groups.

3) Calculate the median x-coordinate and y-coordinate for each group to make points M1, M2, and M3.

4) Find the mean of the x- and y-coordinates of points M1, M2, and M3 to make point P.

5) Calculate the slope of the line that goes through M1 and M3.

6) Find the equation of that line with point P and same slope as M1 and M3.(*Hint* Use the point-slope method)

Already done!

Now you try one! Do question two from the homework sheet

Homework: Question 3 from the sheet (since you should be done the other questions now )