Adam,
OK, seems like you are going with it's always statistical error we just
don't yet know what it is option.
Ed.
On Tue, 2013-03-12 at 16:15 +, Adam Ralph wrote:
Hi Ed,
You can have both types of error in a single experiment, however
you cannot determine
statistical (precision or as Ian says uncontrollable) error with one
experiment. The manufacturer
will usually give some specs on the pipette, 6ul +/- 1ul. In order to
verify the specs
you would need to perform many pipetting experiments. But even if the
manufacturer does not give
any specs you still know that the pipette is not perfect and there
will be a statistical error, you
just do not know what it is.
In theory, accuracy or bias could be determined with one
experiment. Lets say you thought
you had a 6ul pipette but actually it was a 12ul pipette. If you then
compare the 'new' pipette
against a standard you could tell if it was inaccurate. Of course
normally you would repeat
this experiment as well because of statistical error. If detected bias
can be removed. Systematic
error may not be so easily detected. What if the standard is also
biased.
Adam
One can say it's inaccuracy when it is not estimated and imprecision
when it is. Or one can accept Ian's suggestion and notice that
there is
no fundamental difference between things you can control and things
you
can potentially control.
--
Edwin Pozharski, PhD, Assistant Professor
University of Maryland, Baltimore
--
When the Way is forgotten duty and justice appear;
Then knowledge and wisdom are born along with hypocrisy.
When harmonious relationships dissolve then respect and devotion arise;
When a nation falls to chaos then loyalty and patriotism are born.
-- / Lao Tse /
