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GeoGebra Applets - How fancy is too fancy

Page history last edited by LFS 10 years, 9 months ago

FrontPage > GeoGebra Blog > GeoGebra Applets - How fancy is too fancy?

Last updated: 11 December 2009


Question: Does a fancy applet take away from the learning experience or why doesn't the median change?

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I make a BoxPlot and learn about them.

A good GeoGebra friend* began with the BoxPlot Applet for a box-and-whiskers plot.  It had a fixed number of data, namely 10. He then asked me if I knew of a way that he could add data to the spreadsheet so that this data would automatically be re-calculated into the boxplot. My answer was "No, but ..."

Step 1: I could see that the boxplot was from a list generated by the spreadsheet. I will make the list longer with 20 data; the last 10 of which I input 0.

           I do this and define the list: I define Scores20={B2:B21}

Step 2: I seem to recall a list command that takes a subset of another list - sure enough the command Take.

           2a. I define a slider NumberScores from 0 to 20, increment 1.

           2b. I re-define the list Scores=Take[Scores20,1,NumberScores]

So now I should be able to add Scores and by moving the slider get the boxplot to recalculate. Not automatic and not an elegant solution, but workable.

But I had better check it out to see if it works (since I am notoriously careless).

Step 3: Check it out. Everything looks the same as before with NumberScores=10.

           3a. I add an 11th score, i.e. I enter a number in B12 and move my slider to 11. Nothing seems to happen??

           3b. I put the same number in for the 12th score and move my slider to 12. The boxplot changes. 

Whoa - why didn't anything change for 11? Wait, wait - I see the mean changes, but not the boxplot itself (i.e. Q0-Q4 do not change). Hmm. I change the value of the 11th score and move slider between 10 and 11. Still nothing - just the mean. I put in 0 for the 11th score and everything changes. Hmm. I try different values for the 11th score and finally "see" that if I use any number between the whiskers, the boxplot doesn't change. I start to ask myself why? I think about the formulas for Q1, the median and Q2.  Why is it that adding one number doesn't change these values, but adding the same number again changes everything? Is 10 important? I try all different things and then - for fun - I move the slider down to 5, 4, 3, 2, 1.

Learning: Cool beans! What is the minimum number of data to get a box-and-whisker plot in GeoGebra?


Now - at the same time my friend asks me, he also writes to the forum and Murkle gives him a most elegant solution that automatically updates the boxplot as you add data. This is great. But I learned alot about box-and-whisker plots with a not-so-fancy solution. So how fancy do you want your applet?

* see: Prabir's Pad


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