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Abstract This article describes in non-mathematical fashion the technique suggested by H. B. Mann and A. Wald for selecting the number and width of class intervals for the chi-square test of goodness of fit when the null hypothesis distribution is continuous and completely specified. The number of classes is selected by means of a formula depending upon the sample size and the level of significance and the class limits are chosen such that each class contains the same number of items under the null hypothesis. Finally it is suggested that the number of classes as given by the formula may be halved for practical purposes.
Craig Arthur Williams (Wed,) studied this question.