Wendel's theorem explained
In geometric probability theory, Wendel's theorem, named after James G. Wendel, gives the probability that N points distributed uniformly at random on an
-dimensional hypersphere all lie on the same "half" of the hypersphere. In other words, one seeks the probability that there is some half-space with the origin on its boundary that contains all N points. Wendel's theorem says that the probability is
pn,N=2-N+1
\binom{N-1}{k}.
The statement is equivalent to
being the probability that the origin is not contained in the
convex hull of the
N points and holds for any probability distribution on that is symmetric around the origin. In particular this includes all distribution which are
rotationally invariant around the origin.
This is essentially a probabilistic restatement of Schläfli's theorem that
hyperplanes in general position in
divides it into
regions.
[1] Notes and References
- Cover . Thomas M. . Efron . Bradley . February 1967 . Geometrical Probability and Random Points on a Hypersphere . The Annals of Mathematical Statistics . 38 . 1 . 213–220 . 10.1214/aoms/1177699073 . 0003-4851. free .