We are given a multiple regression equation:
The slopes of the regression equation are:
-6 for the variable X1
9 for the variable X2
An interpretation of the slope is:
For each one-unit increase in X1, Y will decrease by 6 units holding X2 constant. For each one-unit increase in X2, Y will increase by 9 units, holding X1 constant.
An interpretation of the intercept is:
The expected mean value of the Y when all X equals zero is 30 units.