Error of measurement and the sensitivity of a test of significance

Implications of random error of measurement for the sensitivity of theF test of differences between means are elaborated. By considering the mathematical models appropriate to design situations involving true and fallible measures, it is shown how measurement error decreases the sensitivity of a test of significance. A method of reducing such loss of sensitivity is described and recommended for general practice.I wish to express my thanks in acknowledgement that the present form of this paper has benefited from editorial comment, and from the advice of Dr. H. Mulhall of the Department of Mathematics, University of Sydney.