Hereditary genius : an inquiry into its laws and consequences / by Francis Galton.

  • Francis Galton
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Hereditary genius : an inquiry into its laws and consequences / by Francis Galton. Source: Wellcome Collection.

    398/424 page 362
    APPENDIX THE deviations from an average are given in the following table of M. Quetelet as far as 80 grades ; they are intended to be reckoned on either side of the average, and therefore extend over a total range of 160 grades. The eightieth isa deviation so extreme, that the chances of its being exceeded (upwards or downwards, whichever of the two ene: we please to select) is only 5:00:90 0—4,999:992 = oa 8y oon or less than one in a million. ‘That is to say, when firing at a target (see Diagram, p. 24) less than one out of a mil- lion shots, taking the average of many millions, will hit it at a greater height than 80 of Quetelet’s grades above the mean of all the shots; and an equally small number will hit 1t lower than the 80th grade below the same mean. Column M gives the chance of a shot falling into any given grade (80 x2 or) 160 in total number. Column N represents the chances from another point of view; it 1s derived directly from M, and shows the probability of a shot lying between any specified grade and the mean ; each figure in N consisting of the sum of all the figures in M up to the grade in question, and inclusive. Thus, as we see by Column M, the chance against a shot falling into the 1st grade (superior or inferior, whichever we please to select) is ‘025225 to 1, and ‘025124 to 1 against its falling into the 2d, and -024924 to 1 against its falling into the 3d; then the chance against its falling between the mean and the third grade, inclusive, is clearly the sum of these 3 numbers, or 075273, which is the entry in Column N, opposite the grade 3.
    digitised image 1
    digitised image 2
    digitised image 3