median
don steward
mathematics teaching 10 ~ 16

Tuesday 12 February 2013

spread


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)

No comments: