Question 4 1 pts You are planning to estimate the effect of X on Y using the model 1110,) = 130 +51X+52W+l333+ 34X X Z Which of the following is true about the way we include W in the regression? ' The BZ coefcient on W tells about the effect of proportional increases in W, not linear increases ' We are allowing the effect of X to be different for different values of W 7 ' The effect of W on Y will be different for different values of W ' We will have closed any back doors that W sits on in our estimate of the effect of X on Y