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Erschienen in:
2022 | OriginalPaper | Buchkapitel
2. Chain Saws
verfasst von : Peter McCullagh
Erschienen in: Ten Projects in Applied Statistics
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Abstract
The second project is a small-scale classically designed experiment that is concerned with comparing efficiencies of chain saws. Duplicate saws of three brands are available for comparison. Logs of three species, pine, spruce and larch, are available as experimental material. Half of the logs are de-barked; the remainder are intact. Six teams are available, ranging in experience from novices to professionals. The response is the time taken by the team to complete a designated task with the saw provided.
The experimental design includes five factors, wood-species, bark, saw-id and saw-brand, and team, but not all combinations of levels because saw-id determines saw brand. It is technically a four-factor fractional factorial design embedded in a 6 × 6 Latin square.
The text first discusses the need for transformation before using linear decompositions. The analysis begins by examining marginal means, and the discussion then centers on ways to compute standard errors for species effects and standard errors for brand effects. The fact that there are only two duplicate saws per brand means that standard errors for brand effects are not computed in the Latin-square standard manner.