Slide 11 of 17
This table shows some results of experiments to estimate sampling error for particle size in Front Range gravel:
1-In the first experiment, the weight pct of gravel > 3/16 inch has a value of 60 wt pct +/- 8 pct, which translates into a value range of 52-68 pct 67 percent of the time.
2- For PCT > Some size, sample errors are typically +/- 2 to 8 pct.
3-These estimates of sampling errors measure the total uncertainty that accompanies sampling and sieving gravel in the Urban Corridor using samples of 40-100 lbs.
3-Although sample errors may seem large, they are important only if they are large relative to the target variance.
U.S. Department of the Interior
U.S. Geological Survey
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Last updated 10 Jan 2013