Regression Lines

1. First you need to go to CATALOG at the bottom of your calculator (2^nd 0) and find DiagnosticOn. 

Press Enter and then Enter again.  You should see Done. 

Now your calculator is set for all the regression problems you will do.  You don’t need to do this step again unless your Diagnostics get turned off.  This “turns on” the r and r-squared values when you do regression.

2. Entering lists

STAT

1:  Edit

Type numbers then hit enter to put them in your lists.

I am using problem 1  Page 113.

For regression you need two lists – they must be exactly the same length or you will get a dimension error.

3. Regression line

STAT

CALC

4 LinReg

Enter

  (2^nd 1)

comma

                        (2^nd 2)

                        comma

                        VARS

                        Y-vars

                        1:  Function

                  1:    

                              Enter

4. Plotting the points

STAT PLOTS (2^nd Y=)

1:  Plot 1…On

Pick the plot    we want the first one the scatterplot

Check the lists and make certain they agree with the ones you used

Now press ZOOM  9:  ZoomStat.

You should see the points and the regression line.

Now that you have the graph you can find any amounts they ask you for.  First check to see if the value you need is in your window.

In part (c) of this question we are asked to find the health care expenditures for 2007.  The x-value is 17 since x = 0 for 1990.  We need to check the window and see if x = 17 is included in the x-values.  My Xmin =-1.3 and my Xmax = 14.3. 

Increase the x-max to at least 17.  I will use 18.

 Now go to CALC (2^nd TRACE).

            1:  value

Enter 17.

            Then press ENTER.

            The answer is 1811.2 billions of dollars in 2007.

The answer in the book is not as exact because they used the rounded off numbers in the equation we found.

Written by B.Anderson