CH A P T E R III
NUMERICAL ANALYS IS OF TH E SERIES
The Frequency
Curves of
indices published
in the
supplement.
Classification
o f features
according
to the
divisions
commonly
used in anthropometry.
T h e classification of the various indices computed from the absolute measurements
which are published in the Appendix was a problem which demanded early consideration.
It was decided that there were certain advantages to be obtained by arranging the indices
in curves of frequency. By this means it was possible to ascertain accurately the
recurrence of the most frequent types, and to observe how far they conformed to the
‘ arithmetical mean ’ or to the ‘ median * of the several series. The identity of each
individual specimen was preserved by entering the catalogue-number of the specimen at
the places in the Frequency-Curves to which its indices assigned i t ; and thus the various
features of any one skull could be followed through the different tables. The employment
of Frequency Curves was all the more convenient as they are essential to the construction
of those Probability Curves to which attention will presently be directed.
It may be well to describe briefly the method of procedure. The paper used was
‘ surveyor’s paper’ which is ruled in squares and may readily be obtained from any
stationer. A base was taken of sufficient length to include the whole range of the index
under consideration, and each square immediately below this base was assigned to one
numerical value of the index, the values being written in serial order. Then on the
verticals above the base, corresponding to the squares below it, were written one by one
the catalogue-numbers of the specimens, each at its proper index-value. In this way
blocks of more or less irregular outline were built up, which formed a record of the
occurrence of the several grades of the different features. The term ‘ curve ’ as applied to
such a figure is somewhat inappropriate, as it suggests a smoothing of the angular outline.
Such a smoothing we never practised, but invariably recorded raw results, as we felt that
it was far better to adhere rigidly to a system which allowed of no personal manipulation.
The outlines of these blocks are represented by a hatched line in Charts i and 11 of the
Supplement, where they are shown in combination with the Probability Curves, which will
be referred to in a later chapter.
For the purposes of classifying the indices the Frequency Curves were divided into
sections corresponding to the main divisions into which the indices are commonly grouped.
The divisions are in the
Cephalic Index .
Vertical Index
Upper Facial (Kollmann’s)
Index .
Dolichocephalic, all below and including 74*9.
Mesaticephalic, 75 to 79-9.
Brachycephalic, 80 and over.
Tapeinocephalic, all below and including 71-9.
Metriocephalic, 72-76-9.
Acrocephalic, 77 and over.
Chamaeprosopic, all below and including 49-9.
Mesoprosopic, between 50 and 54-9.
Leptoprosopic, 55 and over.
TABLE I PERCENTAGE CLASSIFICATION OF INDICES
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A B
BC,
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us
p •oquo ■ US
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I u O " 4 •osayi 1 3 ® 2 £ <8 £ •oquo ■ ’ - s
i 1 •oida-f * •oqU°
W M
Males
Females .
Males . . .
Females
Difference in favour of
Females.
Males
Females .
Males
Females
uinerence in lavour oi
Males . .
Females. . . |
Females .