In a multiple regression analysis involving two independent variables, if b1 is computed to be + 2.0, it means that multiple choice the relationship between x1 and y is significant. the estimated average of y increases by 2 units for each increase of 1 unit of x1, holding x2 constant. the estimated average of y is 2 when x1 equals zero. the estimated average of y increases by 2 units for each increase of 1 unit of x1, without regard to x2.