## Regression

 First enter the data set into the data editor (see data set entry). Note which column of data in the data editor is for the input (independent) variable and which are for the output (dependent) variable. For illustration, we assume that the input data are in list (column) L1 and the output data are in list L2. After data entry, plot (see scatter plot) the data to get a good feel for the regression problem at hand. The displayed example shows the growth of yeast; hence, for our example we conduct a logistic regression.

 Press to access the statistics menu. Press the right arrow on the thumb pad to highlight the CALC menu. The TI-83 can perform a regression to find the equation of best fit for nine different types of equations: cubic, exponential, linear, logarithmic, power, quadratic, quartic, sinusoidal and logistic. We emphasize that only the user can determine the type of function to use.

For our illustration, we find the logistic equation of best fit. Highlight B:Logistic and then press . You are then sent to the home screen with Logistic followed by a blinking cursor.

The logistic information screen is then displayed (see below, left screen). After the regression function is determined, we plot the data with the graph of the regression equation. To view the plot, press to access the zoom menu, then select 9:ZoomStat. If desired, press and adjust the window, then press .

 L1 (located above the 1 key), L2 (located above the 2 key), thumb pad right arrow to highlight Y-VARS (to select 1:Function) (to select 1:Y1)

If the plot shows the graph of an unwanted function, go to the equation editor (Y=) and deselect it by placing the cursor over the highlighted = for that function, then press . Press the thumb pad down arrow and notice that the = is no longer highlighted. Press to view the new graph.

Note All regressions on the TI-83 are done in the same manner as the example given above. The only difference from one problem to another is the data set used and the equation selected for the regression.