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The Importance of Lay-out in Determining Error Variance in Field Experiments

Published online by Cambridge University Press:  03 October 2008

E. A. Roberts
E. A. Roberts
Affiliation:
Biometrical Branch, NSW Department of Agriculture, McKell Building, Rawson Place, Sydney, 2000, Australia
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Summary

Examples are taken from three biometrical texts, two unpublished experiments and Yates (1937) to illustrate quantitatively how the lay-out of the plots can affect the estimate of error variance in field experiments and how confounding of treatment and positional effects can arise. In two examples in which the plots did not run the whole length or width of the block, the estimates of error were reduced by one half and one quarter respectively by allowing for sub-blocks within blocks or for rows and columns. In split-plot experiments where the main plots were split breadthwise, the sub-plot error was about the same size as the main-plot error or larger whereas it is expected to be at most one third that of the main plots when these are split lengthwise. Serious bias can arise in the estimate of treatment effects due to confounding with positional effects; this is illustrated.

Type
Research Article
Information
Experimental Agriculture , Volume 21 , Issue 3 , July 1985 , pp. 223 - 232
Copyright
Copyright © Cambridge University Press 1985

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References

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