**GOAL:** To find "best fit" lines using the technology of
the TI-83

**MATERIALS**

TI-83 calculators

Graph Link

Windows PC

**PROCEDURE**

- Using the TI-83, choose
then enter the data for one variable in List 1 and the other variable in List 2. If you need to delete old information from the lists, highlight, at the top, the list you want to empty, press**Stat, Edit,**and**clear**.**enter** - Set an appropriate window for your graph based on the range of the
data. Choose
from the**ExprOn**menu.**Format** - Choose
and select the first type of graph. Make sure L1 is the Xlist and L2 is the Ylist. Choose squares to mark your graph.**StatPlot, Plot 1, ON** - Press
to see your scatterplot.**Graph** - To get the equation of the "best fit" line (regression
equation), choose
Note: a = slope; b = y-intercept**Stat, Calc, LinReg (ax + b), enter.** - Clear all equations in
Choose**Y =****Y = , Vars, Statistics, EQ, RegEQ, Enter.**

This process will paste the regression equation into themenu. Press**Y =**to see how the line fits.**Graph** - Connect your calculator to the graph link on the computer and open the TI-83 link program.
- With your scatterplot and equation showing on the calculator, choose
Label the window your used on your printout.**Link, Get Screen, 300%, Print.**

**Let's compare our results from yesterday with the TI-83.**

* Example:* The total amount (in millions of dollars) spent
by the government on mathematics research from 1985 through 1995 is shown
in the table. Find the "best fit" line and write its equation.
Predict the amount to be spent in 2000. To center your graph, let x = 0
correspond with 1985.

year |
1985 |
1986 |
1987 |
1988 |
1989 |
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |

amt |
$91 |
$118 |
$128 |
$130 |
$151 |
$184 |
$185 |
$205 |
$212 |
$240 |
$245 |

The point for the average of the coordinates is (5, 171.72)

Another point on the line is (10,245)

slope = (245 - 171.72) / (10 - 5) = 14.7

equation is:

y - 245 = |
14.7(x - 10) |

y - 245 = |
14.7x - 147 |

y = |
14.7x + 98 |

WINDOW [-2, 15] by [-50, 300]

Using yesterday's data, printout results from your TI-83. How did your equations compare?