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$x$ | $y$ |
---|---|

$1$ | $33.12$ |

$2$ | $24.4$ |

$3$ | $16.6$ |

$4$ | $9.3$ |

$5$ | $3.9$ |

The line of best fit can be calculated following these $3$ steps.

1

Enter Values

On a graphing calculator, begin by entering the data points. To do so, press the $STAT $ button and select the option Edit.

This gives a number of columns, labeled $L_{1},$ $L_{2},$ $L_{3},$ and so on.

Use the arrow keys to choose where in the lists to fill in the data values. Enter the $x-$values of the data points in $L_{1}$ and press $ENTER $ after each value. The same can be done for the the corresponding $y-$values in column $L_{2}.$

2

Fitting the Line

After entering the values, press the $STAT $ button and select the menu item Calc.

The option LinReg(ax+b)

gives the line of best fit, expressed as a linear function in slope-intercept form. Press the $ENTER $ button until the parameters are given.

In this case, the line of best fit is described by the function $y=-7.354x+39.506.$ The correlation coefficient $r$ is less than $-0.99,$ indicating a strong negative correlation. If $r$ does not appear, press $2ND $ and $0$ to get to the CATALOG, then select DiagnosticOn

and enable it by pressing $ENTER $ twice. Once more, find the line of best fit.

3

Graphing the Line of Best Fit

A graphing calculator can also be used to graph the line of best fit. After selecting the option LinReg(ax+b),

choose the option Store RegEQ.

Press $VARS $ and move to the **Y-VARS** menu. Then, select the option FUNCTION

and press $ENTER .$

Press the $ENTER $ button until the parameters are given. To graph the scatter plot, first push the buttons $2nd $ and $Y= .$ Then, choose one of the plots in the list. Select the option ON,

choose the type to be a scatter plot, and assign $L_{1}$ and $L_{2}$ as XList

and Ylist,

respectively.

Then, the plot can be made by pressing the button $GRAPH .$ It is possible that after drawing the plot the window-size is not large enough to see all of the information.

To fix this, press $ZOOM $ and select the option ZoomStat.

After doing that, the window will resize to show the important information.