Susan, I am certain this is my fault but I don't understand what you 
are saying here - can you have another try? :)

I understand the differene between accuracy and precision, and the 
different types of precision.

What I don't understand is this bit:


>
>Now, having reviewed quite a bit of evidence on this topic, NO ONE 
>HAS REALLY TESTED PRECISION except for dependability.  Dependability 
>plagues all assessments.  If you assess a baby using any tool 
>included your eyeballs only once -- you have not really covered the 
>dependability issue -- be it swallows, diapers, behavior, or weight. 
>It is dangerous practice not to actively listen to what the mother 
>is telling you and follow up. 
>
>Embedded in the original article, after four years of contemplating 
>the fact that the education in mathematics and statistics is so 
>abysmal that even a peer reviewed journal cannot even spot a GLARING 
>error such as mistaking what actually was a very poor test of 
>accuracy for a test of precision -- I found a very telling one line 
>sentence in the original article. 
>
>The authors THOUGHT they were testing evaporative water loss. 
>Evaporative water loss is basically sweat loss.  They actually did 
>repeat their measurements of test weighing.  They concluded that 
>evaporative water loss was unimportant.  What they actually 
>conducted was a test of precision.  The median and the interquartile 
>range of the differences between these estimates was ---- get this 1 
>g.  Now PLEASE tell me how one can conclude that a repeat measure 
>with only 1 g of difference even with evaporative water loss is 
>IMPRECISE?   By their own study results their repeatability was at 
>least as good a within 1 g of the original estimate.  I have found 
>repeatability of eyeballing the volume of milk in a bottle to be off 
>by much much more.


thanks!

Heather Welford Neil
NCT bfc, tutor UK, and sadly, literature and languages graduate (in 
Italian) and a late comer to science :)
-- 
http://www.heatherwelford.co.uk

http://heatherwelford.posterous.com

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