Curve fitting may involve either interpolation[4] or smoothing.[5] Using interpolation requires an exact fit to the data. With smoothing, a "smooth" function is constructed, that fit the data approximately. A related topic is regression analysis,[6][7] which focuses more on questions of statistical inference such as how much uncertainty is present in a curve that is fit to data observed with random errors.
Fitted curves can be used to help data visualization,[8][9] to guess values of a function where no data is available,[10] and to summarize the relationships among two or more variables.[11]Extrapolation refers to the use of a fitted curve beyond the range of the observed data.[12] This is subject to a degree of uncertainty,[13] since it may reflect the method used to construct the curve as much as it reflects the observed data.
↑S.S. Halli, K.V. Rao. 1992. Advanced Techniques of Population Analysis. ISBN0306439972 Page 165 (cf. ... functions are fulfilled if we have a good to moderate fit for the observed data.)