Education Technology

Solution 34855: Calculating a Median-Median Regression on the TI-84 Plus Family of Graphing Calculators. 

How do I calculate a Median-Median Regression on the TI-84 Plus family of graphing calculators?

Med-Med (median-median) fits the model equation y=ax+b to the data using the median-median line (resistant line) technique, calculating the summary points x1,y1,x2,y2,x3 and y3. Med-Med displays values for a (Slope) and b (y-intercept).

The following example will demonstrate how to calculate a Med-Med regression:

X= {15; 25; 50; 50; 75; 80; 95}
Y= {4; 9; 20; 31; 55; 42; 73}

Key the data into the handheld:

• Enter STAT edit mode by pressing [STAT], [1].
• Enter the data in the L1 and L2 lists, pressing [ENTER] after each entry.
• Press [2nd] [QUIT] to leave the editor.

To calculate the Med-Med line, please follow the steps below:

• Enter the STAT mode again by pressing [STAT].
• Select CALC.
• Press 3 to select Med-Med.
• Press [ENTER] to get the Xlist and Ylist.

• Select Calculate and press [ENTER] to perform the regression calculation.

To set up the Stat Plot, please follow the steps below:

• Press [2nd] [STAT PLOT].
• Choose [1:Plot1].
• Select ON and press [ENTER].
• Select Scatter Plots and press [ENTER].
• Make Xlist = L1 and Ylist = L2.

Note: Mark may be set to the first setting.

To graph the linear regression, please follow the steps below:
• Press [Y=] the cursor should be beside Y1=.
• Press [VARS] down to [5:] Statistics [ENTER].
• Scroll to EQ press [1: RegEQ].
• Press [GRAPH].
• Press [ZOOM] and select [ZOOMSTAT] and press [ENTER].

Please see the TI-84 Plus Family guidebooks for additional information.