Math 120 - Finite Mathematics

Calculator Instructions
    Linear Regression
       TI-82 or TI-83

This sheet is designed to give you instruction on how to compute the (best-fit) linear regression line on your graphing calculators.

Scenario: Data is collected from six students in a psychology class. Each student is questioned about the number of hours he/she studies a week and his/her GPA (on a 5 point scale).  

The data is treated as a set of ordered pairs and plotted in the following graph to visually investigate patterns.

Upon visual investigation, the data appears to have a linear trend or pattern. This does not mean that you could draw a single straight line that would pass through all the points. In fact, for this data, you could not.

Our next step is to find the equation of a line that best “fits” the data. This line is called cleverly enough, the best-fit or linear regression line.

The best-fit line has the form y = mx + b where m, the slope, and b, the y-intercept are obtained using statistical formulas. In this class, we will find the best-fit line using our graphing calculators!

Linear Regression: Steps on the Calculator

1. Entering the data in the calculator as ordered pairs

The data for the students must be organized as a set of ordered pairs, where the input value (x value) corresponds to the number of hours the student studied and the output value (y value) corresponds to the student’s GPA. Our set of order pairs looks like this:

{ (2, 1.5), (7, 2.5), (7, 3.5), (9, 3), (10, 3.5), (12, 4) }

To enter the ordered pairs in the calculator press:

I.  Press

II. Press

III. Enter the ordered pairs in L₁ and L₂ using the display below as your guide.

2. Find the equation of the best-fit line

I. Get back to the home screen. Press     to get to the home screen.

II. Press  and use the right arrow  to get to the CALC menu.

III. Press  and     so the calculator will produce the best-fit line.

Conclusion: Equation of the best-fit line is:  y = .23796x + 1.13598