don steward
mathematics teaching 10 ~ 16

Tuesday, 12 February 2013


these four small data sets have the same mean
and the same mean absolute deviation

hopefully prompting some rationale for the invention of the standard deviation - which, as well as making negative deviations positive, exaggerates these differences 

the standard deviations (2 decimal places) are fairly close:
(a) 1.90
(b) 2.28
(c) 2.53
(d) 1.79

so sorting them into a rank order is not that easy a task!
the ranges give a reasonable rank order but don't distinguish between (a) and (d)

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