The relationship of Y to four other variables was established as Y = 12 + 3X1 - 5X2 + 7X3 + 2X4. When X1 increases 5 units and X2 increases 3 units, while X3 and X4 remain unchanged, what change would you expect in your estimate of Y?

Unchanged

None of the above

Increase by 15

We should never manipulate more than one independent variable in a multiple regression model