Meaning of Interpolation and Extrapolation

Interpolation is a method of estimating the most probable  missing figure on  the basis of given data under certain assumptions. On the other head if such figure is required   to be  estimated  for the future period   outside the series, it  is called extrapolation .In the words of Hirish. Interpolation  is the estimating of a most likely estimate under given conditions. The  technique  of estimating  a past  figure  is termed as interpolation , while estimating  for future is called  extrapolation, W.M. Harper has  defined  as interpolation consists in reading  a value  which  lies between  two extreme points. Extrapolation  means reading a values  that lies outside the two  extreme points.