Because of the risk of lead poisoning, the exposure of children to lead-based paint is a significant public health concern. The first step in the quantitative analysis of lead in dried paint chips is to dissolve the sample. Corl evaluated several dissolution techniques.24 In this study, samples of paint were collected and pulverized with a Pyrex mortar and pestle. Replicate portions of the powdered paint were then taken for analysis. Results for an unknown paint sample and for a standard reference material, in which dissolution was accomplished by a 4–6-h digestion with HNO3 on a hot plate, are shown in the following table. (a) Determine the overall variance, the variance due to the method, and the variance due to sampling. (b) What percentage of the overall variance is due to sampling? (c) How might the variance due to sampling be decreased?
Because of the risk of lead poisoning, the exposure of children to lead-based paint is a significant public health concern. The
first step in the quantitative analysis of lead in dried paint chips is to dissolve the sample. Corl evaluated several dissolution techniques.24 In this study, samples of paint were collected and pulverized with a Pyrex mortar and pestle. Replicate portions of the powdered paint were then taken for
analysis. Results for an unknown paint sample and for a standard reference material, in which dissolution was
accomplished by a 4–6-h digestion with HNO3 on a hot plate, are shown in the following table.
(a) Determine the overall variance, the variance due to the method, and the variance due to sampling.
(b) What percentage of the overall variance is due to sampling?
(c) How might the variance due to sampling be decreased?
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