humanfaculty4 - page 58 of 305

Inquiries into Human Faculty

larger amount of that quality. I have called this the method of statistics by

intercomparison. There is no bodily or mental attribute in any race of

individuals that can be so dealt with, whether our judgment in comparing

them be guided by common-sense observation or by actual measurement,

which cannot be gripped and consolidated into an ogive with a smooth

outline, and thenceforward be treated-in discussion as a single object.

It is easy to describe any given ogive which has been based upon

measurements, so that it may be drawn from the description with

approximate truth. Divide AB into a convenient number of fractional

parts, and record the height of the ordinates at those parts. In reproducing

the ogive from these data, draw a base line of any convenient length,

in the same number of fractional parts, erect ordinates of the

stated lengths at those parts, connect their tops with a flowing line, and the

thing is done. The most convenient fractional parts are the middle (giving

the median), the outside quarters (giving the upper and lower quartiles),

and similarly the upper and lower octiles or deciles. This is sufficient for

most purposes. It leaves only the outer eighths or tenths of the cases

undescribed and undetermined, except so far as may be guessed by the run

of the intermediate portion of the curve, and it defines all of the

intermediate portion with as close an approximation as is needed for

ordinary or statistical purposes.

Thus the heights of all but the outer tenths of the whole body of adult

males of the English professional classes may be derived from the five

following ordinates, measured in inches, of which the outer pair are

67.2; 67.5; 68.8; 70.3; 71.4.

Many other instances will be found in the Report of the

Anthropometric Committee of the British Association in 1881, pp. 245—

When we desire to compare any two large statistical groups, we may

compare median with median, quartiles with quartiles, and octiles with

octiles; or we may proceed