The use of a formula, deduced from an initial set of data, for data values outside the range of the initial data set. Compare interpolation. Excessive extrapolation may give unreliable values and is not recommended.
For example, if we discover that 1 kg of fertilizer per ha results in a yield of 50 kg of produce per ha, that 1.5 kg gives 60 kg, and that 2 kg gives 70 kg, then we might reasonably extrapolate that 2.5 kg would give 80 kg. However, it would be excessive extrapolation to expect 10 kg to give 230 kg.