Determining a Line of Best Fit(using a graphing calculator)

Goal: Determine an equation for a line of best fit using a graphing calculator and define the squared deviation for the

determined equation.

Warm Up

There are 3 steps you need to take in order to plot points on a calculator, what are they? (Feel free to use your graphing calculator guide)

1. Turn Plot 1 On (2nd – Stat Plot)2. Enter your data under L1 and L2 (STAT – Edit)

3. Adjust your window4. Press Graph

Enter this data under L1 and L2

Press STAT

Enter this data under L1 and L2

Press “Edit”

Enter this data under L1 and L2

Enter this data under L1 and L2

Enter this data under L1 and L2

Enter this data under L1 and L2

Return to the home screen (2nd – Quit/Mode)

Press “STAT”

Press the right arrow to highlight CALC and choose the function “LinReg”.

Press the right arrow to highlight CALC and choose the function “LinReg”.

Press “Enter” to get the equation.

Round each number to the nearest thousandth (three decimal places) & substitute them into the equation “ax+b” to get an equation for a line of best fit.

y = 0.240x + -400.989

THIS IS YOUR EQUATION FOR THE LINE OF BEST FIT!!!!!!

To get prepared for tomorrow we will find the deviations between data found using this equation and the original data. To start, go back to your “Lists”

(Stat – Edit) and highlight “L3”.

Press Enter and you will see a blinking cursor at the bottom.

Enter your equation where the cursor is blinking, substituting L1 for x.

Press Enter.

To determine the deviations, highlight L4 and press enter so you have the blinking cursor again. This time enter L2-L3.

Press Enter to get the deviations.

The deviations must be squared, so highlight L5, press Enter, and insert (L4)2 to square the deviations.

The deviations must be squared, so highlight L5, press Enter, and insert (L4)2 to square the deviations.

Determine the Line of Best Fit and find the squared deviations for this set of data:

Line of Best Fity = 19.796x + 95.111

Squared Deviations3.568312.2010.0106140.94722.9920.1672830.393

Closure

Why would I want to square my deviations? What would be

the point in that?