Statistics shows that if you put a large number of<unk><unk>  on a bounded flat surface you can find many<unk> .  Some people think that this can be used to prove that ley lines exist due to chance alone (as opposed to supernatural or anthropological explanations).
One precise definition which expresses the generally accepted meaning of "alignment" as:
"Straight path of width w" may be defined as the set of all<unk>  within a distance of w/2 of a straight line on a plane, or a great circle on a sphere, or in general any geodesic on any other kind of manifold.  Note that, in general, any given set of<unk>  that are aligned in this way will contain an uncountable number of infinitesimally different straight paths.  Therefore, only the existence of at least one straight path is necessary to determine whether a set of<unk>  is an<unk>  For this reason, it is easier to count the sets of<unk> , rather than the paths themselves.
The width w is important: it allows the fact that real-world features are not mathematical<unk> , and that their positions need not line up exactly for them to be considered in<unk> 
For example, using a 1 mm pencil line to draw<unk>  on an 1:50,000 Ordnance Survey map, a suitable value of w would be 50 m.
Alignments of random points
Degrees of freedom 
Equation of state
Covariance matrix
Quantum yield
Algorithms for calculating variance
Ancillary statistic
Hund's rule of maximum multiplicity