# Using TI graphing calculators

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Using TI graphing calculators
Regression tutorial Using TI graphing calculators

The regression feature of a graphing calculator can be used to find mathematical models for sets of data. Suppose we want to find a linear equation to model or “fit” the data in this table: 8 5 3 1 y 4 2 x

To enter the data Press STAT Select EDIT by pressing ENTER
If you already see data listed in the L columns, you must clear it. Click here for directions to clear previous data.

8 5 3 1 y 4 2 x To enter the data Enter the values of the independent variable in the first column, pressing ENTER after each one. This should be L1

8 5 3 1 y 4 2 x To enter the data Use the arrow keys to move the cursor to the second column, L2 L1 and L2 are called lists. Enter the values of the dependent variable in the second column beside the corresponding numbers in the first column, pressing ENTER after each one.

Caution! You must have the same number of entries in each column or you will get a DIM MISMATCH error

To plot the data points Clear any functions entered in the Y= list or they will be graphed along with your data points. Press STAT PLOT (2nd Y=) Press ENTER 2nd MODE(to leave that screen)

To plot the data points Move the cursor to highlight ON and press ENTER If any settings differ from the ones show on the right, correct them by using your arrow keys

To plot the data points Choose a window to fit the values in your data lists. You can also press ZOOM, #9(STAT) Press GRAPH

To calculate a regression equation
Press STAT Move to CALC

To calculate a regression equation
Choose the type of regression you want for your equation. LINREG is for a linear function, EXPREG is exponential, etc. In this example, use the arrow keys to highlight LINREG Press ENTER to select

To calculate a regression equation
Press ENTER again The calculated numbers for the regression are on the home screen The regression equation is y = 2.3x – 1.5

To graph the regression equation You can type in the equation in your Y= menu OR pull it from memory as described below: Follow the procedure to calculate a regression equation Press Y= Press VARS Press #5 Move Cursor to EQ Select #1: RegEQ

To graph the regression equation
Press ENTER This brings the regression equation to Y1

To graph the regression equation
Press GRAPH and you will see the data points as well as the graph of the regression equation.

To clear data in the stats lists
Use the arrow keys to move the cursor on top of the L1 column and press CLEAR (not DELETE). Repeat for L2. Do NOT press DELETE. This will delete the whole column, not just the data. (click here to return to tutorial)

Reminder Be sure to go back and turn the STAT PLOT off when you are ready to go back to “regular” function graphing. Press 2nd STAT PLOT, press ENTER Move over to highlight OFF and press ENTER again.