A randomly distributed microphone array is considered in this work. In many applications exact design of the array is impractical. The performance of these arrays, characterized by a large number of microphones deployed in vast areas, cannot be analyzed by traditional deterministic methods. We therefore derive a novel statistical model for performance analysis of the MWF beamformer. We consider the scenario of one desired source and one interfering source arriving from the far-field and impinging on a uniformly distributed linear array. A theoretical model for the MMSE is developed and verified by simulations. The applicability of the proposed statistical model for speech signals is discussed.