Problem bank

Problem 291 of 333MediumLinear AlgebraP291

Orthogonalizing a factor before the regression

  1. Over four days you observe returns (in %) for the market mm, a momentum factor ff, and a stock yy. Treat all series as mean zero and fit without an intercept.

    m=(1,1,−1,−1),f=(2,0,0,−2),y=(5.5,−0.5,−1.5,−3.5)m = (1, 1, -1, -1), \quad f = (2, 0, 0, -2), \quad y = (5.5, -0.5, -1.5, -3.5)
    • Regress yy on ff alone. What is the slope?
    • Remove from ff its projection onto mm, call the result f⊥f_\perp, and regress yy on f⊥f_\perp. What is the slope?
    • Fit yy on mm and ff together. What are the two coefficients and the residual vector?

    Which of the first two slopes equals the joint momentum coefficient, and why?