Select five arbitrary data values for your linear regression line. Select the independent variable for the x coordinates and the dependent values for the y coordinate. Use the number of oranges eaten per week as the independent x value, and the number of cavities per year as the dependent y value. Use the following paired data points (1, 5), (2, 4), (3, 3), (4, 2), (5,0) to represent orange consumption data per week and cavity rate per year. Observe that this fictional data suggest that the more oranges you eat per week, the fewer cavities you will get per year.
Press the "On" key on your calculator. Press the "Apps" key. Scroll with the cursor keys (set of four keys on the upper right side of your calculator) through the applications menu on the screen until you reach the Data/Matrix application. Use the "up," "right," "left" and "down" cursor keys to scroll on the screen. Press the "Enter" key when the cursor is over the "Data/Matrix" application (indicated by the icon turning black).
Select choice "3," called "New" on the display screen. Type in the name for the data table you will create in the "Variable" text box. Use the "Alpha" key to enter alphabetical typing mode. Refer to the alphabetical labels above the keys to locate the letters you want to type for the name of your data table. Press "Enter" after you have typed in the name.
Enter in the x, y data points in the data table. Enter the first x data point in the C1 column and the first y data point in the C2 column. Continue in the same fashion for all five points.
Press "F5" to access the TI-89's calculation menu. Select "linReg" from the menu that appears. Press the "Enter" key.
Write down the numerical value of "a" and "b" that is listed on the screen. Call "a" the slope of the best fit linear regression line. Call "b" the y-intercept of the best fit linear regression line.