Friday, August 09, 2013

Quartiles

(Click on the cartoon to see the full image.)

To be fair, only one student shouted that. I pretended not to hear it.

Breta said...

That's wrong, lower quartile is 4,75!

(x, why?) said...

No, 9 divided by 2 is 4.5.

What method are you using to arrive at that?

Breta said...

You can check it in some software, for example in Microsoft Excel or Statsoft Statistica and it will give you number 4.75. However, you can't do classic average of 4 and 5, but you must take account of that 4 is quantile on p=0,181818... and 5 is quantile on p=0,2727... so quantile on p=0,25 (our lower quartile) is closer to 5. With simple calculation (i.e. Cross-multiplication) you find right value 4.75.

(x, why?) said...

Or you can realize that what you are doing is absolutely ridiculous on a data set with 12 elements in it.

But feel free to alert me when you have rewritten all the high school Algebra books to use your approach ... As well as when you have wolframalpha reprogrammed, as it agrees with me on what the quartiles are. And quartiles are what I teach to high school freshmen, not p=0,25 quantiles.

Otherwise, someone will be awfully busy grading old Regents exams going back probably decades.

Have a nice evening.