A new approach to the concept of a strong unified-least-squares matrix Original Research Article

For given matrices A, B, C, and D of appropriate sizes, a criterion for the range of the product AB−C to be a subspace of the range of D irrespective of the choice of a generalized inverse B− of B is established. This result is crucial in a new approach to the concept of the strong unified-least-squares matrix, which plays an essential role in the theory of estimation in the general Gauss–Markov model.