Abstract :
The idea of significance testing underlies most practical applications of probability theory to electrical measurements. This paper discusses the problems involved in the application of simple tests of significance to small sets of measurements. It opens with an account of the w-test, which is designed to apply to normally distributed variables. This is followed by a description of the t-test, which is of particular use in dealing with a small number of observations. A method of rapidly applying this test is given, and it is shown that if the true mean value of a physical quantity is unknown the confidence limits to be attached to an estimated value obtained from the measurements may be easily determined. The paper describes a rapid method of estimating the standard deviation of a set of measurements; it is shown that for very small samples the extreme-mean or median forms a good alternative to the arithmetic mean and is often easier to calculate. Pearson´s ¿2-test of goodness-of-fit is explained and illustrated. Emphasis is placed on the flexible nature of this test and its relationship to the w-test.
