The usual S 2 chart is constructed with equal false alarm probabilities for the lower and upper control limits. An alternative is the ARL-unbiased S 2 chart, where the ARL (average run length) curve attains its maximum when the common-cause variance is at its in-control value. We examine the ARL properties of these S 2 charts, and show that neither the usual S 2 chart nor the ARL-unbiased S 2 chart is optimal in a natural sense. We propose two criteria, under which optimal S 2 charts can be constructed. The effects of parameter estimation on our designs are also discussed, and suggestions are made regarding practical implementation.
A table and a procedure are given for finding the multiple deferred (dependent) state sampling plans of type MDS-(cl, cz) involving minimum sum of producer's and consumer's risks for spectjied acceptable quality level and limiting quality level.
The haematology and biochemistry changes observed in cattle infected with T. orientalis Ikeda type were consistent with extravascular haemolytic anaemia. Adult dairy cattle were more likely to be severely anaemic than calves. There were differences in haematology and biochemistry profiles between adult dairy cattle and calves, but most of these differences likely had a physiological rather than pathological basis. Overall, the haematological changes in calves aged <6 months appeared less severe than in adult dairy cattle.
This paper extends the concept of chain sampling to variables inspection when the standard deviation of the normally distributed characteristic is known. A discussion of the shape of the known sigma single-sampling variables plan is given. The chain sampling plan for variables inspection will be useful when testing is costly or destructive.
We address several theoretic issues involved in the design of geometric control charts. Primary among these is the question of setting probability limits, based on notions of "unbiasedness" and "conditional power". A nearly ARL-unbiased design is defined by setting the in-control ARL as near as possible, given the discrete nature of the geometric distribution, to the peak of the ARL curve. An optimal design criterion, based on minimizing the sum of out-of-control ARLs for upward and downward shift is also suggested. These are shown to produce improved conditional power compared with the usual design.
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