This is an external advisory service for third party products. This service is usually requested by the management of a program evaluation unit. It may be required when there is doubt or disagreement regarding an evaluation deliverable. It may serve as a mediation service, as when there is professional disagreement on the quality expectations of a delivered evaluation product. It may be the provision or a written expert opinion on a delivered product. It may deal with some specific element (for example, to which population do the results of a survey’s data sample generalize) or the entire study (for example, the confidence to be placed in the presented findings of an evaluation).