An Introduction to the theory of statistics

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Monograph

Identifikator:: 1751730271

URN:: urn:nbn:de:zbw-retromon-127610

Document type:: Monograph

Author:: Yule, George Udny http://d-nb.info/gnd/12910504X

Title:: An Introduction to the theory of statistics

Edition:: 8. ed. rev

Place of publication:: London

Publisher:: Griffin

Year of publication:: 1927

Scope:: XV, 422 S; Ill., Diagr

Digitisation:: 2021

Collection:: Economics Books

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Document type:: Monograph

Structure type:: Chapter

Title:: Part II. The theory of variables

Collection:: Economics Books

THEORY OF STATISTICS. however, be chosen, for simplicity in classification, so that no limit corresponds exactly to any recorded value (cf. § 8 below). In some exceptional cases, moreover, the observations exhibit a marked clustering round certain values, e.g. tens, or tens and fives. This is generally the case, for instance, in age returns, owing to the tendency to state a round number where the true age is unknown. Under such circumstances, the values round which there is a marked tendency to cluster should preferably be made mid-values of intervals, in order to avoid sensible error in the assumption that the mid-value is approximately representative of the values in the class. Thus, in the case of ages, since the clustering is chiefly round tens, ¢ 25 and under 35,” “35 and under 45,” etc., the classification of the English census, is a better grouping than ¢ 20 and under 30,” «30 and under 40,” and so on (cf. the Census of England and Wales, 1911, vol. vii., and also ref. 5, in which a different view is taken). When there is any probability of a clustering of this kind occurring, it is as well to subject the raw material to a close examination before finally fixing the classification. 1. Classification.—The scale of intervals having been fixed, the observations may be classified. If the number of observations is not large, it will be sufficient to mark the limits of successive intervals in a column down the left-hand side of a sheet of paper, and transfer the entries of the original record to this sheet by marking a 1 on the line corresponding to any class for each entry assigned thereto. It saves time in subsequent totalling if each fifth entry in a class is marked by a diagonal across the preceding four, or by leaving a space. The disadvantage in this process is that it offers no facilities for checking: if a repetition of the classification leads to a different result, there is no means of tracing the error. If the number of observations is at all considerable and accuracy is essential, it is accordingly better to enter the values observed on cards, one to each observation. These are then dealt out into packs according to their classes, and the whole work checked by running through the pack corresponding to each class, and verifying that no cards have been wrongly sorted. 8. In some cases difficulties may arise in classifying, owing to the occurrence of observed values corresponding to class-limits. Thus, in compiling Table I., some districts will have been noted with death-rates entered in the Registrar-General’s returns as 16-5, 175, or 185, any one of which might at first sight have been apparently assigned indifferently to either of two adjacent classes. In such a case, however, where the original figures for numbers of deaths and population are available, the difficulty may be readily surmounted by working out the rate to another place 20

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