The mental and physical life of school children / by Peter Sandiford.

  • Sandiford, Peter, 1882-1941.
Date:
1913
Catalogue details

Licence: In copyright

Credit: The mental and physical life of school children / by Peter Sandiford. Source: Wellcome Collection.

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    parents a black-liaired child, and stupid parents a brilliant child. In general, however, variations obey two laws : (1) The law of distribution in a form resembling that of mere chance ; (2) The law of regression towards the normal of the species or race. (1) The law of chance may best be illustrated by an example. Suppose that all the men (10,000) of a given town were arranged in a long row beginning with the shortest and ending with the tallest. We should find that a line joining the tops of the heads would rise sharply at first, then remain almost horizontal for a long time, and finally take another sharp turn near the end. The reason for this is obvious ; there are but few very tall or very short men in a given community, the majority are of “ average ” height. If we represented each man by a line]we should get a figure somewhat like the following : The peculiarly shaped curve obtained by drawing a smooth line through the tops of the perpendiculars is known as an ogive. A more usual way of representing such facts graphically is shown by Fig. 3. The curve is obtained by plotting out the numbers of men whose heights fall between the various consecutive inches. It is known in statistics as a Normal Distribution Curve ; a Normal Surface of Frequency; a Curve of Chance ; or a Gaussian Curve. Such a curve could be obtained experimentally by plotting, in similar manner, the numbers of “ heads ” obtained when thirty coins are tossed a very