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Graphing Calculators are the New Slide Rule

Updated: Sep 12, 2023

Fancy calculators allow our statistics students to do a whole lot of statistics that would be very tedious to do by hand. Unfortunately the user interface with calculators has changed very little over the last 20 years and is now far behind other technology.

Let me try to make my case. Today in class I wanted students to make a scatterplot, find the line of best fit, and make a residual plot.

Option 1: Graphing Calculator

Make scatterplot:

  • STAT/EDIT/Edit

  • Enter values for the explanatory variable in List 1.

  • Enter values for the response variable in List 2.

  • 2ND/Y=/ON/Scatterplot/L1/L2/ZOOM/Zoomstat

Find line of best fit:

  • STAT/CALC/LinReg(a+bx) L1,L2,Y1 (VARS/Y-VARS/Function/Y1)

Make residual plot

  • 2ND/Y=/On/Scatterplot/L1/RESID (2ND/STAT/NAMES/RESID)

  • ZOOM/ZoomStat

Over 30 (memorized) keystrokes. And then I get a scatterplot and a residual plot with no axis labels or scale on either axis.  Model once for the students, then have students help each other learn the calculator, then spend the rest of the hour helping out individual struggling students.

Option 2 (The Better Option): Applet

  • Go to the 2 Quantitative Variables applet.

  • Type in GPA for explanatory and ACT for response and add values.

  • Click “Begin Analysis”.

  • Click “Calculate least-squares regression line”.

Two clicks. Zero (memorized) keystrokes. And then I get a beautiful scatterplot and a residual plot with axis labels and scaled axes.  Model once for the students, then allow them the rest of the hour to work through an activity that explores residual plots for several different data sets.

More time for thinking and reasoning about statistics

When using the graphing calculator to make residual plots, I spent half of the lesson making sure that all students learned the more than 30 keystrokes needed to make the graphs. The next day in class was spent reducing anxiety about calculator familiarity. Instead of wasting this valuable instructional time on calculators, now I can focus on the content. What makes this line the “best fit”? What does the residual plot tell us about the line of best fit? What would the residual plot look like for nonlinear data?

No more memorizing keystrokes

Because applets were designed within the lifetime of our students (and not prior) the user interface is very intuitive. Johnny Student clicks through applets as quickly as he does through SnapChat or Twitter. This allows students to focus on the thinking and reasoning behind the statistics. Rather than memorizing keystrokes, students are pondering the meaning of a pattern that shows up in the residual plot.

Nicer graphs

Calculators produce floating dots on a screen. Applets provide a context (axis labels) and a scale. Check out the graphs for this GPA vs. ACT data.

TI Calculator:


Where do I go on the Internet?

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Carter Scarbrough
Carter Scarbrough

I completely understand and agree with your reasoning for students using an applet instead of the calculator to learn about residual plots. However, when teaching AP Statistics, will they not need to know how to create a residual plot (preferably with technology) for the AP Exam? This is only my second year teaching AP Stat, so I could definitely be wrong, but I was under the impression that students need to be able to create residual plots for the exam and they definitely will not have access to any applets then. In that case do you tell your students to make the plots by hand?


I was wondering the same thing!

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