A procedure for replacing the discrete set of results obtained from an experiment by a continuous function. It is defined by the following. For the set of variables there are measured values such as and it is decided to write a relation: where are undetermined constants. If it is assumed that each measurement of has associated with it a number characteristic of the uncertainty, then numerical estimates of the are found by constructing a variable , defined by and solving the equations obtained by writing except . If the relations between the and are linear, this is the familiar least-squares technique of fitting an equation to a number of experimental points. If the relations between the and are non-linear, there is an increase in the difficulty of finding a solution, but the problem is essentially unchanged.