2. A set of n subjects give data on a response variable y and two non-random regressors, x, and x2 . The data are fitted to the model y = dot a(X1 - X1) + a2(X2 - X2) + 8 where xx is the simple average of Xx values from this set of data, k = 1, 2; & is a random error with mean zero. Discuss the conditions under which OLS estimators can be obtained for the coefficients of the regressors x1 and x2 . Discuss the conditions under which statistical tests can be constructed for testing statistical significance of the individual regressors