REGRESSION Polynomial Regression (Page 1 of 4)

There are two other polynomial regression models available on the TI-83/84. Let's try a cubic regression model, which will be a polynomial of degree three. The process is similar to that of the linear or quadratic models. Since the data is already entered and graphed, all we need to do is compute the model. It is called CubicReg, and it is also located in the STAT CALC submenu. Following the command, specify the lists that contain the x-values (L1) and y-values (L2).

 2nd QUIT key. CLEAR key.

 STAT key. [CALC] 6: menu selection. 2nd L1 key. Comma key. 2nd L2 key.
 Comma key. VARS key. [Y-VARS] 1: menu selection. 1: menu selection. ENTER key.

 Calculator screen image. Calculator screen image.

The general form of the model is shown, as well as the values of each parameter used in the model (a, b, c and d). For this example, the equation is y = 0.075x^3-1.054x^2+8.536x-9.297. The correlation coefficient r is not displayed, but instead R-squared, which is the coefficient of determination.
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