Final report of the Anthropometric Committee / F. Galton, Chairman.

Date:
[1883]
Catalogue details

Licence: Public Domain Mark

Credit: Final report of the Anthropometric Committee / F. Galton, Chairman. Source: Wellcome Collection.

    5/74 (page 3)
    Methods. 10. The forms and instruments used have been explained in the Reports for 1878 and 1880 ; but practical difficulties have been found to exist in obtaining trustworthy observations with regard to breathing capacity. Experience has also led the Committee to believe that the use of Snellen’s test-types for sight, Nos. 1 and 10, is more convenient, and will yield more trustworthy results, than that of the army test-dots, which were adopted in its original circulars.1 Since 1879, also, the Com¬ mittee has introduced the use of cards for recording the observations relating to single persons, which has been extensively adopted in Ger¬ many and the United States, and recently by the Investigation Com¬ mittee of the British Medical Association, and which offers great facilities in analysing and grouping the facts observed. The Committee appends copies of the forms of the cards and of the methods of measurement and observation which they have employed. (See Appendix A.) 11. The difference between the average and mean of a number of obser¬ vations, and its importance in dealing with the subjects under considera¬ tion, has been pointed out and discussed by Mr. Roberts in the Report for 1881, at p. 233 ;2 and the special sense in which Mr. Roberts employs the term mean, being that value in an arithmetic series of observed values of which the observations are the most frequent, has been adopted by the Committee.3 12. In connection with the question of the applicability of the expo¬ nential law of error to statistical results relating to anthropometry, Mr. Francis Galton has contributed a valuable series of tables, with remarks, on the range in height, weight, and strength, in which he introduces his method of the calculation of deciles, quartiles, and medians.4 bias, the correctness of the scale with which the measures are compared, and the assurance that we have the entire range of error, at least in one direction, within the record.’—Sir J. F. W. Herschel, Edin. Rev. vol. xcii. 1 See the Report for 1881 for a discussion of this subject by Mr. Lawson and Mr. Roberts. „ , 2 Also in a note at p. 121 of the Report for 1880. 3 Mr. Roberts has followed Quetelet in the use of the word mean, and its differ¬ ence from an average is thus explained by Sir John Herschel. Speaking of Quetelet’s homme moyen he says :—‘ Now, this result, be it observed, is a mean as distinguished from an average. The distinction is one of much importance, and is very properly insisted on by M. Quetelet, who proposes to use the word mean only for the former, and to speak of the latter (average) as the “ arithmetical mean.” .... An average may exist of the most different objects, as of the height of houses in a town, or the size of books in a library. It may be convenient to convey a general notion of the things averaged, but involves no conception of a natural and recognised central magnitude, all differences from which ought to be regarded as deviations from a standard. The notion of a mean, on the other hand, does imply such a conception, standing distinguished from an average by this very feature, viz., the regular march of the groups, increasing to a maximum and then again diminishing. An average gives us no assurance that the future will be like the past. A mean may be reckoned on with the most implicit confidence. All the philosophical value of statistical results depends on a due appreciation of this distinction, and acceptance of its con¬ sequences.’— Edin. Rev. vol. xcii. Mr. Galton, however, desires to state that con¬ sidering many statistical groups which are regular in their distribution are at the same time normally asymmetrical, he does not recognise the expressions of ‘mean value ’ and ‘ the value most likely to be observed ’ as strictly equivalent. 4 Report for 1881, p. 245.