Linear Regression


The linear regression option finds the equation of a linear equation of the form y = ax + b or y = a + bx that best fits a set of data. First, enter the data . Press  .



Press  and use  to select CALC. Press  This yields an equation of the form y = ax + b.

 


The linear regression option can also be obtained by pressing . This yields an equation of the form y = a + bx.

 


The resulting equations are equivalent, y = 0.24x + 1.14 and y = 1.14 + 0.24x. The TI-83 calculates the correlation coefficient, r. In this case, r is about 0.91. The value of r lies between -1 and 1, inclusive. It is a measure of how well the regression equation fits the data. A value of -1 or 1 indicates a perfect fit. It also calculates the value of the coefficient of determination, r2.

The TI-83 stores the regression equation. The equation can be graphed and is transfered to  without typing the equation as follows. Press    and use  to select EQ.



Press . The equation is now entered in . Press . The data points can also be viewed. Access STAT PLOTS by pressing  . To turn the plots on press .




Note: The resulting linear equation is an exact fit if two nonvertical data points are entered.

The TI-83 calculates the correlation coefficient r and the value of r2, the coefficient of determination.