SEDL / STP / STP114-EB / STP43979S

Economic Accumulation of Variance Data in Connection with Bulk Sampling

Tanner, Louis
Chief, and Assistant Chief Chemist, U. S. Customs Laboratory, Boston, Mass.

Lerner, Melvin
Chief, and Assistant Chief Chemist, U. S. Customs Laboratory, Boston, Mass.

Pages: 5    Published: Jan 1952

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Abstract

Estimates of two variances, between and within, must be available in order to employ the technique for establishing sampling schedules for bulk materials discussed in the paper by Tanner and Deming, “Some Problems in the Sampling of Bulk Materials,” (1). Frequent or continuous redetermination of these variances is necessary to establish the continued applicability of a sampling schedule. When each secondary unit is inspected individually in routine operations, continuous data are available at no extra cost. But when testing is expensive, samples are usually composited, in which case the variance data are lost. A plan is discussed whereby these data may be made available for variance estimates even though samples are composited for economy in testing.