In mathematics, estimation of a value between two known data points.
A simple example is calculating the mean (see mean, median, and mode ) of two population counts made 10 years apart to estimate the population in the fifth year. Estimating outside the data points (e.g., predicting the population five years after the second population count) is called extrapolation. If more than two data points are available, a curve may fit the data better than a line. The simplest curve that fits is a polynomial curve. Exactly one polynomial of any given degree
an interpolating polynomial
passes through any number of data points.