Most graphing calculators have a function called *linear regression* which can be used to find a precise line of fit, using strict rules. This line of fit is then called the line of best fit or the regression line.

### Enter values

The first step is to enter the data points in the calculator. On a TI calculator, this is done by first pressing the STAT button, and then selecting the option Edit....

This gives a number of columns, marked L$1$, L$2$, L$3,$ etc.

With the help of the arrow keys, choose where in the lists to fill in the data values. Enter the data points' $x$-values in list L$_1,$ and the corresponding $y$-values in L$_2.$ Values are entered into the fields using the number buttons followed by ENTER.

### Fitting the line

After entering the values, press the STAT button, then select the menu item CALC to the right.

The option LinReg(ax+b) gives a line of best fit, expressed as a linear function in slope-intercept form.

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