'Equation 20.6 (on page 616) gives the ML estimators for the parameters 1, 2, 2 1, 2...

'Equation 20.6 (on page 616) gives the ML estimators for the parameters µ1,

µ2, σ2 1, σ2 2, and σ12 in the bivariate-normal model with some observations on X2 missing at random but X1 completely observed. The interpretation of µb1 and σb2 1 is straightforward: They are the available-case mean and variance for X1. Noting that S'

12=S2'

1 is the complete-case slope for the regression of X2 and X1, offer interpretations for the other ML estimators.