# Linear Regressions on TI Graphing Calculators

//Linear Regressions on TI Graphing Calculators
Linear Regressions on TI Graphing Calculators 2019-09-24T12:33:19+00:00

If you type data into your calculator and it appears to be linear, it can find the equation of the line for you.  This process is called performing a linear regression.

### Calculator Set Up

1. Make sure that your calculator has the Plots Off, Y= functions cleared, the MODE and FORMAT are set at “stage left”, and the lists are cleared.
2. Turn the Diagnostics on.
• Press 2nd the CATALOG (2nd of 0).  Press the teal D button (ALPHA of x-1)  This brings you to the items in the catalog that start with D.
• Arrow down until you reach the command DiagnosticOn and press ENTER.
• Press ENTER a second time.  Later, when you perform a linear regression, you will see an “r” value.  If that value is close to a ±1 there’s a strong correlation to the data, meaning the data points can be modeled by the line well.

### Enter the Data

Data for this lab will be stored in L1 and L2.

• Press the STAT menu and choose option 1:Edit…
• Type the first value in the L1 table, then press ENTER, type the second value next, and so forth.
• Arrow over to the L2 table and enter the corresponding dependent values
• Make sure there is an equal amount of data in both L1 and L2 so you don’t get a “dim mismatch” error.

### Performing a Linear Regression

• To view your data, you must set up a stat plot. Press 2nd STAT PLOT (2nd of Y=).  Press
ENTER
to set up Stat plot 1.  Set up your stat plot to look like the one at the right.  Then press the ZOOM key and choose option 9:ZoomStat.
• To find an equation that matches the data you see, you need to perform a linear regression on the data. Press the STAT menu and arrow to the right to the CALC menu.  Choose option 4:LinReg (ax+b).  Type L1, a comma, L2, then the VARS button, arrow over to Y-VARS, choose 1:Function, the 1:Y1 option, then press ENTER.

When you press the GRAPH button a line that matches your data points will also be in your viewing window.  Pressing the Y= button will give you the equation of that line.

Let’s have the calculator find the line of best fit for wing length vs. wing-beat rate.

 Flamingo Shell Duck Velvet Scooter Fulmar Great Egret Wing Length (mm) 400 375 281 321 437 Wing-Beat Rate (bps) 2.4 3.0 4.3 3.6 2.1