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
But the same principles will also supply a caution in
the case of the last example. They remind us that, for
the mere purpose of comparison, the _average_ man of any
group or class is a much better object for selection than
the eminent one. There may be greater difficulties in the
way of detecting him, but when we have done so we have
got possession of a securer and more stable basis of comparison.
He is selected, by the nature of the case, from
the most numerous stratum of his society; the eminent
man from a thinly occupied stratum. In accordance therefore
with the now familiar laws of averages and of large
numbers the fluctuations amongst the former will generally
be very few and small in comparison with those amongst the
latter.
1. _Essai de Physique Sociale_, 1869. _Anthropométrie_, 1870.
2. As regards later statistics on the same subject the reader can
refer to the Reports of the Anthropometrical Committee of the
British Association (1879, 1880, 1881, 1883;--especially this
last). These reports seem to me to represent a great advance on the
results obtained by Quetelet, and fully to justify the claim of the
Secretary (Mr C. Roberts) that their statistics are "unique in range
and numbers". They embrace not merely military recruits--like most
of the previous tables--but almost every class and age, and both
sexes. Moreover they refer not only to stature but to a number of
other physical characteristics.
3. As every mathematician knows, the relative numbers of each of these
possible throws are given by the successive terms of the expansion
of (1 + 1)^{10}, viz. 1, 10, 45, 120, 210, 252, 210, 120, 45, 10, 1.
4. That is they will be more densely aggregated. If a space _the size
of the bull's-eye_ be examined in each successive circle, the number
of shot marks which it contains will be successively less. The
_actual_ number of shots which strike the bull's-eye will not be the
greatest, since it covers so much less surface than any of the other
circles.
5. Commonly called the exponential law; its equation being of the form
y = Ae^{-hx^{2}}. The curve corresponding to it cuts the axis of y
at right angles (expressing the fact that near the mean there are a
large number of values approximately equal); after a time it begins
to slope away rapidly towards the axis of x (expressing the fact
that the results soon begin to grow less common as we recede from
the mean); and the axis of x is an asymptote in both directions
(expressing the fact that no magnitude, however remote from the
mean, is strictly impossible; that is, every deviation, however
excessive, will have to be encountered at length within the range of
a sufficiently long experience). The curve is obviously symmetrical,
expressing the fact that equal deviations from the mean, in excess
and in defect, tend to occur equally often in the long run.
[Figure: Gaussian normal distribution.]
Public-domain text, read in full here on John Shaqi.
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