Approximation
Approximation (approximation - approximation) is a procedure for selecting an optimal approximating function from a specified class of functions. It is important to distinguish between parametric and nonparametric approximation. In parametric approximation, the general form (formula, model) of the studied relationship is considered known, and it is necessary to estimate the values of parameters. Parametric approximation provides a good approximation if the model corresponds well to reality, i.e., is adequate. In nonparametric approximation, only the most general information about the studied relationship is considered known. In this case, it is necessary to select from the given class a function that would be close in some sense to the true function. Nonparametric approximation is a tool for studying complex and little-studied relationships when there is insufficient information to develop a parametric model
Source: "ANALYSIS OF AGE-SPECIFIC MORTALITY RISKS OF THE POPULATION. METHODOLOGICAL RECOMMENDATIONS"
(approved by the Ministry of Health of Russia on 22.01.2001 No. 11-3/25-09)