In simple regression the dependent variable Y was assumed to be linearly related to a single variable X. In real life, however, we often find that a dependent variable may depend on more than one independent variable. A simple example is the idea of profit. The profit of a company would depend upon a number of revenues and costs. Hence, the simple regression equation appears to be inadequate in representing such a situation.
In general the multiple regression equation is
where there are k independent variables X1, X2,---- Xk.
We can also write the equation as = A + B1x1 + B2x2 + .... + Bnxk + Ε