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Working with Two-Variable Data on the TI-83(82)
This paper will discuss using the TI-83 to display and analyze data. First we will look at the mechanics of using the calculator to get a plot. Then we will discuss some methods of fitting a curve to the data and measuring the quality of the fit.
Editing Data
To edit data use the STAT key. Then select from the menu. There are six lists L 1 ,
L 2 , … L 6 that can be used to store data. Use the cursor keys to move from list to list and up
and down in a list.
Erasing Data
In the first picture on the right there is data in L 1 and L 2.
To erase this data, move the cursor over the name of the list at the top of the screen (see first picture).
Then press CLEAR ENTER.
Do the same for each list. The result is the second picture.
Entering New Data
To enter data, move the cursor to the place in the list you want the value, type the value and press ENTER. Note that the value is not put in the list until after the ENTER key is pressed. You can change values by typing over them. To delete a value use the DEL key.
To insert a value use 2nd INS to get into the insert mode.
In the example to the right L 1 is the year and L 2 is the VCC enrollment. (0 means 1970, 5 is 1975, etc. ) It is always a good idea to restate year data using smaller numbers as we did in this example.
The Regression Command
Before finding the regression equation you must go to the catalog and turn the “Diagnostics On”. You only have to do this once and then never again. This will you to see the value of the correlation coefficient, r. The catalog is on top of the 0 button. Scroll down using the arrow buttons until you see DiagnosticOn. Make sure the arrow is next to DiagnosticOn, then press enter, and enter again. It should just say Done. Again, this is a one time only process.
The regression line can be calculated on the TI-83 under STAT [Calc] menu. Next, you specify which lists the x and y data are in. L1 can be found on top of the 1 key, L on top of the 2 key and so on. See figures 9, 10, 11 below.
Figure 9 Figure 10 Figure 11
To graph the regression line we can manually enter the equation into Y 1 or add one
more argument to the linear regression command. Start the same as before: STAT [Calc] menu, and then L1, L2. Next enter a comma and Y1, found under VARS [Y- Vars] [Function]. This will automatically store the regression equation in Y1.
Notice that there are other regression types built into the TI-83.
QuadReg fits a quadratic function f(x) = ax^2 + bx + c CubicReg fits a cubic function f(x) = ax^3 + bx 2 + cx + d QuartReg fits a quartic function f(x) = ax^4 + bx 3 + cx 2 + dx + e LnReg fits a logarithmic function f(x) = a + bLn(x) ExpReg fits a exponential function f(x) = a(bx^ ) PwrReg fits a power function f(x) = axb
