# Why is linear interpolation and extrapolation not useful in making predictions?

##### 1 Answer

Feb 21, 2015

**Linear interpolation** is not useful in making predictions because it only suggests data values within an already known range (typical within time). For example, if you knew data values for the years 1980, 1990, 2000, and 2010, **interpolation** could be used to determine likely values between 1980 and 2010 (that's what interpolation means).

**Linear extrapolation** is normally not useful in making predictions because so very few time based function are linear in nature and, even in "near future" predictions graphs of values like stock market prices are not smooth.