Ian,
On Wed, 2013-03-13 at 19:46 +0000, Ian Tickle wrote:
> So I don't see there's a question of wilfully choosing to ignore. or
> not sampling certain factors: if the experiment is properly calibrated
> to get the SD estimate you can't ignore it.
>
So perhaps I can explain better by using the same example of protein
concentration measurement. It is certainly true that only taking one
dilution is "poor design". (Although in crystallization practice it may
not matter given that it is not imperative to have a protein exactly at
10 mg/ml, 9.7 will do). If I don't bother including pipetting precision
in my error estimate either by direct experiment or by using
manufacturer's declaration I am willfully ignoring this source of error.
That would be wrong.
But what if I only have one measurement worth of sample? And pipetting
precision cannot be calibrated (I know it can be so this is hypothetical
- say pipettor was stolen and company that made it is out of business,
their offices burned down by raging mob). Is the pipetting error now
systematic because experimental situation (not design) prevents it from
being sampled or estimated?
I actually like the immutable error type better for my own purposes, but
I am trying to see whether some argument might stand that allows some
error that can be sampled to be called inaccuracy nonetheless.
Cheers and thanks,
Ed.
--
I don't know why the sacrifice thing didn't work.
Science behind it seemed so solid.
Julian, King of Lemurs
