The Logic of Chance, 3rd edition: An Essay on the Foundations and Province of the Theory of Probability, With Especial Reference to Its Logical Bearings and Its Application to Moral and Social Science and to StatisticsVenn, John
Philosophy
The Logic of Chance, 3rd edition: An Essay on the Foundations and Province of the Theory of Probability, With Especial Reference to Its Logical Bearings and Its Application to Moral and Social Science and to Statistics
Venn, John
Chance; Logic, Symbolic and mathematical; Probabilities; Science -- Methodology
I have collected statistics including over 13,000 male and female
births, arranged in families of four and upwards. They were taken from
the pedigrees in the Herald's Visitations, and therefore represent as
a rule a somewhat select class, viz. the families of the eldest sons
of English country gentlemen in the sixteenth century. They are not
sufficiently extensive yet for publication, but I give a summary of
the results to indicate their tendency so far. The upper line of
figures in each case gives the _observed_ results: i.e. in the case
of a family of four, the numbers which had four male, three male and
one female, two male and two female, and so on. The lower line gives
the _calculated_ results; i.e. the corresponding numbers which would
have been obtained had batches of M.s and F.s been drawn from a bag in
which they were mixed in the ratio assigned by the total observed
numbers for those families.
512 families of 4; | m^4 m^3 f m^2 f^2 mf^3 f^4
yielding | 81 + 148 + 161 + 98 + 24 (observed.)
1188 M. : 860 F. | 57 + 168 + 184 + 88 + 15 (calculated.)
512 families of 5; | m^5 m^4 f m^3 f^2 m^2 f^3 mf^4 f^5
yielding | 50 + 82 + 161 + 143 + 61 + 15 (obs.)
1402 M. : 1158 F. | 25 + 103 + 172 + 143 + 59 + 10 (calc.)
512 families of 6; | m^6 m^5 f m^4 f^2 m^3 f^3 m^2 f^4 mf^5 f^6
yielding | 30 + 48 + 115 + 146 + 126 + 40 + 7 (obs.)
1612 M. : 1460 F. | 10 + 56 + 133 + 159 + 108 + 41 + 5 (calc.)
The numbers for the larger families are as yet too small to be worth
giving, but they show the same tendency. It will be seen that in every case
the observed central values are less than the calculated; and that the
observed extreme values are much greater than the calculated. The results
seem to suggest (so far) that a family cannot be likened to a chance drawing
of the requisite number from _one_ bag. A better analogy would be to suppose
two bags, one with M.s in excess and the other with F.s in less excess, and
that some persons draw from one and some from the other. But fuller
statistics are needed.
It will be observed that the total excess of male births is large. This
_may_ arise from undue omission of females; but I have carefully confined
myself to the two or three last generations, in each pedigree, for greater
security.
1. _Essay on Probabilities_, p. 114.
Public-domain text, read in full here on John Shaqi.
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