equation (redirected from equations of the second order)
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equation a means of portraying arithmetically the relationship between VARIABLES. For example, the equation: C = 1,000 + 0.9Y suggests a particular relationship between consumer expenditure (C) and disposable income (Y), which would be true for certain values of C and Y (such as 10,000 and 10,000 respectively) but not true of other values of C and Y (such as 6,000 and 10,000 respectively). Equations are generally written with a two-bar equals sign (=), with the value to the left of the sign being equal to the value to the right of the sign. The validity of an equation can be tested statistically by collecting paired observations of the variables involved and testing whether or not these observations conform with the equation formulated. See IDENTITY.