Order restricted randomized designs and two sample inference |
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Authors: | Omer Ozturk Steven N MacEachern |
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Institution: | (1) Department of Statistics, The Ohio State University, 404 Cockins Hall, 1958 Neil Ave., Columbus, OH 43210, USA |
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Abstract: | This paper develops a new design that relies on subjective judgment ranking to compare subsets of experimental units. This
judgment ranking is used along with restricted randomization to improve statistical inference for the contrast between two
levels of a treatment. The new design assigns the judgment ranked units in a subset to different treatments. Such an assignment
translates the positive dependence among units within each subset into negative dependence for the estimators of treatment
means, and hence leads to a reduction in variance for the contrast. For the proposed design, a test for the difference in
means of two treatment levels is developed along with an associated confidence interval. It is shown that the null distribution
of the proposed test is approximated reasonably well with the Student’s t-distribution for sample sizes as small as 6. A simulation study indicates that the proposed design is advantageous compared
to its competitors in the literature for both high and low quality rankings. The new design’s advantage increases with the
quality of rankings. |
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Keywords: | Completely randomized design Contrast estimation Judgment ranking Ranked set sampling t-Test |
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