Slide 10 of 17
These examples illustrate error variance. Any sampling procedure produces error.
1-Channel sampling of gravel is shown on the left. Repeated sampling of the same channel cut in gravel will yield samples having slightly different values for a characteristic, such as average particle size.
2-Repeated measurement of a characteristic, such as would be obtained by re-sieving a sample to determine average particle size, will yield different results, also. The differences measure the error of the sieve method.
3-Error variance is the sum of sampling and measurement.
U.S. Department of the Interior
U.S. Geological Survey
This page is <URL: http://pubs.usgs.gov/of/1998/ofr-98-0332/sld010.htm>
Site Maintainers: Randy
Schumann and Gene
For more information about this report contact: David A. Lindsey
Last updated 10 Jan 2013