Stan, Here is a further clarification of precision and accuracy.
>From a set of measurements of the same quantity under the same circumstances, >each measurement deviates from the mean value of the measurements, and the >square root of the mean of the deviations is called the standard deviation >from the mean as a measure of the precision of the measurements. Whether an odometer *displays* decimal values to one, two, or three digits (to an *apparent* accuracy of one meter) does not determine either precision or accuracy of a measurement of distance by an odometer. A set of a reasonably large number of readings of the same distance by the same odometer is necessary to determine the precision of the odometer (as mounted in its carrier vehicle). The mean value of the odometer measurements (and its standard deviation) compared with an independent measurement of the same distance (perhaps by a laser device) then can be used as a measure of the comparative accuracy of the odometer mean value of the distance. This may seem complicated, but these procedures are necessary to realize the full requirements of precision and accuracy with respect to an odometer. A single reading does not determine either precision or accuracy. Gene. ---- Original message ---- >Date: Sun, 25 Jan 2009 18:50:45 -0500 >From: "STANLEY DOORE" <[email protected]> >Subject: [USMA:42568] Re: An Associated Press article in today's Atlanta >Journal-Constitution >To: "U.S. Metric Association" <[email protected]> > > Pat et al: > > Let's clarify the distinction between accuracy > and precision. > Two decimal place odometer readout is precision > but it says nothing about how accurate that readout > number is. > Stan Doore
