Control Charts for Measurements with Varying Sample Sizes
- 1 July 1969
- journal article
- research article
- Published by Taylor & Francis in Journal of Quality Technology
- Vol. 1 (3) , 163-167
- https://doi.org/10.1080/00224065.1969.11980368
Abstract
When sample sizes vary, analysis by control charts must be modified from that for equal sample sizes. A simple weighted average of the X̄'s, with weights n, is taken for X̄ in general. Usually when n's are small, ranges R are used. Then to estimate σ for the process (if variabilities are indeed homogeneous) an unweighted average of the unbiased estimates, R/d2, has commonly been used. This paper provides two systems of simple weights from which better results are obtainable. Similarly, weights for sample standard deviations are also given.Keywords
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