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An Application of the Balanced Lattice Design in a Feeding Trial with Swine^{1, 2}

North Carolina Agricultural Experiment Station

Abstract

A balanced lattice design was used, probably for the first time, in a feeding trial with swine. Since nine rations were being compared, variation stemming from litter differences would otherwise have contributed to experimental error.

The efficiency of the design relative to a randomized complete block was 121 percent. This gain in efficiency is very close to what can be expected on the average from similar applications of this type of design in trials where the treatment effects are to be measured in terms of rate of gain. It is not sensational but is worthwhile, particularly since the only cost involved is a slight increase in labor of analyzing the data of the experiment. Fortunately, there is no danger that use of a lattice design will lead to a less efficient experiment.

When using experimental material in which variance from sources other than litters, e.g., breed differences, can be confounded with the differences between incomplete blocks, the gain may be appreciably greater than in this instance.

In view of the general efficiency inherent in the comparison of more rations in a single trial and of the value of factorial experiments in many problems, there should be frequent occasions for the use of lattice designs in swine feeding work.

¹ Contribution from the Departments of Experimental Statistics and Animal Industry, North Carolina Agricultural Experiment Station. Published with the approval of the Director as Paper No. 273 of the Journal Series.

² This investigation was aided by a Swift & Company fellowship.