highly significantp < 0.01
74 X 4 2 The developed polynomial equation suggested that the linear (X 2 , X 3 , and X 4 ), interactive (X 1 X 4 , X 2 X 3 , X 2 X 4 , and X 3 X 4 ), and quadric terms ( X 1 2 , X 3 2 , and X 4 2 ) are highly significant ( p < 0.01).