Previous sensor/observer performance prediction models have not explicitly treated false alarm effects, especially in relation to clutter. A method for predicting probabilities of detection as a function of observer false alarm probability and clutter is presented. The method is applied to previously collected observer data to determine the effect of observer false alarm probability on resolution criteria associated with specified clutter levels. The interdependent effects of clutter and observer false alarm probability are illustrated by deriving an expression for the probability of target acquisition in the case where the observer has only enough time to select one target candidate. It is concluded that false alarm probability has a significant impact on target resolution criteria in moderate and high background clutter. Example resolution criteria are given for several false alarm probabilities.