In mathematics, extrapolation is the process of estimating,
beyond the original observation interval, the value of a
variable on the basis of its relationship with another variable.
It is similar to interpolation, which produces estimates between
known observations, but extrapolation is subject to greater
uncertainty and a higher risk of producing meaningless results.
Extrapolation may also mean extension of a method, assuming
similar methods will be applicable. Extrapolation may also apply
to human experience to project, extend, or expand known
experience into an area not known or previously experienced so
as to arrive at a (usually conjectural) knowledge of the unknown
(e.g. a driver extrapolates road conditions beyond his sight
while driving). A sound choice of which extrapolation method to
apply relies on a prior knowledge of the process that created
the existing data points. Some experts have proposed the use of
causal forces in the evaluation of extrapolation methods.
Crucial questions are for example