Below is the design matrix for an ANOVA of two groups each with two observations. Calculate by hand the hat matrix H = X (X^T X)^{-1}X^TH=X(XTX)?1XT.

X design matrix for 2 groups of 2 observations - O with treatment coding Hint : For a 2 x 2 matrix A - we have A"= 1 d - b ad - bc - c a