Using the Calculator to Graph Scatter Plots

Everything we just learned about Scatter Plots we will now do with the calculator. Plot points Plot points Find a line of best fit Find a line of best fit Write the equation of the line Write the equation of the line

Entering in Data to your Calculator Press the STAT key Press the STAT key Select menu item 1 “Edit” Select menu item 1 “Edit” Enter x values into L1 Enter x values into L1 Enter y values into L2 Enter y values into L2 Shoe size Height (in)

Set up the scatter plot Press 2 nd  STAT PLOT (located above the Y= button) Press 2 nd  STAT PLOT (located above the Y= button) Select Plot1 by pressing “ENTER” Select Plot1 by pressing “ENTER” Make sure that the “ON” is selected. Make sure that the “ON” is selected. Type should be the first option, the scatter plot. Type should be the first option, the scatter plot. Also make sure that you screen says… Also make sure that you screen says…  Xlist : L1  Ylist : L2

Setting a window for your data Press window Press window Set your x-min a little smaller than your smallest values in L1 Set your x-min a little smaller than your smallest values in L1 Set your x-max a little bigger than your biggest values in L1 Set your x-max a little bigger than your biggest values in L1 Set your y-min a little smaller than your smallest values in L2 Set your y-min a little smaller than your smallest values in L2 Set your y-max a little bigger than your biggest values in L2 Set your y-max a little bigger than your biggest values in L2

Graph Press the “GRAPH” button to see your scatter plot. Press the “GRAPH” button to see your scatter plot.

Line of Best Fit Press the “STAT” button Press the “STAT” button Cursor over to CALC Cursor over to CALC Select option 4:LinReg(ax+b) Select option 4:LinReg(ax+b) As long as our x values are in L1 and our y values are in L2 all we have to do is hit enter. As long as our x values are in L1 and our y values are in L2 all we have to do is hit enter. This returns values for a, b, r, and r 2 make sure you write these down. This returns values for a, b, r, and r 2 make sure you write these down.

What is r? r is called the “Correlation Coefficient” r is called the “Correlation Coefficient” r tells us how good of a line it is. r tells us how good of a line it is. If the r value is close to 1 or -1 the data is closely correlated and the line fits the data well. If the r value is close to 1 or -1 the data is closely correlated and the line fits the data well. An r value close to 0 means that the two sets of data don’t have a very linear relationship and the line is a lousy predictor of the behavior of the data. An r value close to 0 means that the two sets of data don’t have a very linear relationship and the line is a lousy predictor of the behavior of the data.

Draw the line of best fit Write down the equation y=ax+b using the a and b from the previous step. Write down the equation y=ax+b using the a and b from the previous step. Press the “Y=“ button Press the “Y=“ button Enter the equation into Y1 and press graph. Enter the equation into Y1 and press graph.