“…In addition to this, internal evaluators are often asked to change evaluation plans by senior managers dealing with changing organizational conditions: ''Unlike an external evaluation which is based on a negotiated contract, internal evaluators, even when an evaluation plan is negotiated, must be prepared to change that plan'' (Mathison, 1991a, p. 174). Although the ability to quickly change established evaluation plans to suit organizational needs is a definite advantage of internal evaluation, such modifications are resource-intensive and can sometimes negatively affect the credibility of evaluation studies and therefore hinder their use (Lyon, 1989).…”