Regression (TI 83)

Goal: We wish to determine a "closest" function of a given form to the points represented by a list of ordered pairs (the data points).

Preliminaries:We will proceed with an example that finds the best fit to our data points in the form of a 3rd degree polynomial.

Assume that the data is represented in two lists. The first list, L1, contains the x-coordinates (in order) of our data points and the second list, L2, contains the y-coordinates.

Step by step method:

• STAT/EDIT/1:EDIT
• Move the cursor (with arrow keys) to the heading of a vacant column. Enter L1 as the x-list name. In a second column, enter L2 as the y-list name.
• Move to the first entry under L1 and enter the x-coordinates down this column. Fill L2 in a similar manner. EXIT
• STAT/CALC Choose P3Reg followed by the L1 and L2 names (comma separated)
• Produced, is a list named PRegC containing coefficients of regression ploynomial from coeff of x^3 downward
• To put the regression polynomial in y1, enter the y(x)= menu, place cursor after \y1= and enter RegEq (You can type this in or find it under STAT/VARS )

Remark: Other function forms are available at the point where P3Reg is chosen.

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