[at-l] Voodoo Science - Statistics.

[m_factor@hotmail.com (Mara Factor)]

Hi Steve,

The statistic you're looking for is median, not mean.  The mean is the
average while the median is the 50th percentile around which half will be
above and half below.

It is possible for all but one child to be below average for any given
distribution.

Here are some, admitedly contrived, examples:

If four children get a 50 and one child gets an 80, the average will be
((4*50)+(1*80))/5=3D56.  In this case 4 children are below average and only
one child above.

To better illustrate median, imagine if the children got scores of 20, 30,
40, 80, and 90.  The median will be 40 as it's the "middle" number.  If the
scores were 1,2,3,4,5,90, and 100, the median would be 4.

It is proper to say that 50% of children fall below the median, however, yo=
u
better have the proof before you claim that half are below average.

Mara - who no longer supports statistical analysis software.  ;-)

>From: "Steve Adams" <stephensadams@hotmail.com>
>To: shane@theplacewithnoname.com
>CC: at-l@mailman.backcountry.net
>Subject: [at-l] Voodoo Science - Statistics.
>Date: Tue, 10 Dec 2002 20:48:53 -0500
>
>Shane,
>
>Reference your post, dated 12-10-02,  relating your "favorite statistical
>=91lie.'
>
>My favorite statistical truth goes as follows:
>
>Approach an educator (they used to be "teachers") or someone else concerne=
d
>with education (parents of school age children are of course excellent).
>Looking earnest and concerned, somberly ask, "Do you realize that almost
>half the students in our schools are below average?"
>
>Of course they are.  The definition of "average" requires 50% to be below
>average, just as it requires 50% to be above average.  Just don't get
>caught
>talking about the modal average.
>
>For some reason, few people readily catch on to this.  They look so
>perplexed when I wander off, chuckling.  People think I'm weird.  Not
>enough
>humor in this world.
>
>Steve
>


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