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    Author(s): Floyd A. Johnson
    Date: 1961
    Source: PNW Old Series Research Notes No. 201, p. 1-6
    Publication Series: Research Note (RN)
    Station: Pacific Northwest Research Station
    PDF: Download Publication  (210 KB)


    This report assumes a knowledge of the principles of point sampling as described by Grosenbaugh, Bell and Alexander, and others.

    Whenever trees are counted at every point in a sample of points (large sample) and measured for volume at a portion (small sample) of these points, the sampling design could be called ratio double sampling. If the large sample is either a completely random or a systematic sample of the area being cruised, and if the small sample is either a completely random or a systematic sample from the large sample, formula 1 (below) is appropriate for calculating an estimate of average volume per acre. Formula 1 is already available in the literature on point sampling, and is shown here merely to introduce the standard error of estimated average volume (formula 2) which is not well known. Formula 2 is strictly appropriate only for completely random samples. If used with systematic samples, it must be considered an approximation.

    Publication Notes

    • Visit PNW's Publication Request Page to request a hard copy of this publication.
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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Johnson, Floyd A. 1961. Standard error of estimated average timber volume per acre under point sampling when trees are measured for volume on a subsample of all points. PNW Old Series Research Notes No. 201, p. 1-6

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