SUMMARYThe capability index, C pm , sometimes called the Taguchi index, has the desirable characteristic of being sensitive to both dispersion and deviation of the process average from the engineering target. As a result, the proposed estimators of C pm have a sampling distribution that is dependent on the non-central chi-square distribution. Hence, constructing confidence intervals, performing hypothesis testing or estimating sample size requirements necessitates manipulation of a rather complex functional expression, typically beyond the capabilities of practitioners who need readily available tools. Here, a simple graphical procedure is proposed and illustrated for obtaining exact confidence intervals for C pm . The graphical procedure allows the user to simply enter the graph with an estimate of the index and a value of the non-centrality parameter for a given sample size to arrive at end-points of 90%, 95% or 99% one-sided or two-sided confidence intervals. Detailed tables are also provided to assist the user for a wider range of sample values and sample sizes. In addition, a procedure is also presented for determining the minimum sample size required for attaining a pre-specified level of accuracy of the C pm . Extensive tables are provided for the user with a simple example illustrating the facility of the technique. Copyright
A method for sampling from bulked eucalypt seed for germination tests, and a special technique for testing germination of these seeds in Petri dishes are described. The seeds of Eucalyptus camaldulensis Dehn. will germinate both at constant and at alternating temperatures. They germinate best at a constant temperature of about 95°F. The seeds require light for satisfactory germination. The light requirements of all seed-lots tested were satisfied by 8 hours of light daily at a constant temperature of 95°F. Light requirements are least at temperatures close to 95°F. There is an interaction between light and temperature and the requirement for light is reduced as the temperature is increased. Stratification also reduces the requirement for light in germination. Thirty-one different lots of seeds have been studied. It has been shown that no relationship exists between environmental conditions of the locality of collection and optimum conditions for germination.
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