SEVEN-FACTOR CENTRAL COMPOSITE DESIGN ROBUST TO A PAIR OF MISSING OBSERVATIONS
In this work, the seven-factor central composite design (ııı) is studied in respect of a pair of missing values using the minimax loss criterion. It was observed empirically that seven-factor central composite design with k = 7 ,n = 128 , = 14 ,n = 3 and n = 145 is robust at a = 2.6 and variance robust at a = 2.45. We also observed that the loss effect of missing a pair of factorial points is a decreasing function of increasing a , while the loss effect of a pair of axial points is a decreasing and increasing function of increasing a . The loss effect of missing a factorial and axial points has no specific direction of increase or decrease on increasing a values.