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380
Hereditary Genius
These columns may be used for two purposes.
The one is to calculate a table like that in p. 34, where I have simply
lumped 11 of Quetelet's grades into I, so that my classes A and a
correspond to his grade 11 in column N, my classes B and b to the
difference between his grades 22 and 11, my C and c to that between
his grades 33 and 22, and so on.
The other is as a test, whether or no a group of events are due to
the same general causes; because, if they are, their classification will
afford numbers that correspond with those in the table; otherwise,
they will not. This test has been employed in pp. 30, 31, and 33. The
method of conducting the comparison is easily to be understood by
the following example, the figures of which I take from Quetelet. It
seems that 487 observations of the Right Ascension of the Polar Star
were made at Greenwich between 1836 and 1839, and are recorded
in the publications of the Observatory, after having been corrected
for precession, nutation, &c., and subject only to errors of
observation. If they are grouped into classes separated by grades of
0.5 sec. the numbers in each of these classes will be as shown in
Column III. page 380. We raise them in the proportion of 1, 000 to
487 in order to make the ratios decimal, and therefore comparable
with the figures in Quetelet's table, and then insert them in Column
IV. These tell us that it has been found by a pretty large experience,
that the chance of an observation falling within the class of — 0.5
sec. from the mean, is 150 to 1, 000; of its falling within the class of
— 1.0 sec. is 126 to 1,000; and so on, for the rest. This information is
analogous to that given in Column M of Quetelet's table, and we shall
now proceed to calculate from IV. the Column V. which is analogous
to Quetelet's N. The method of doing so is, however, different. N
was formed by adding the entries in M from the average outwards;
we must set to work in the
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