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 +0000, 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 /
