Program evaluation is the systematic investigation of the worth or merit of a program. Program evaluation can provide evidence of achievement of program goals and purposes, identify effective program components, determine the reasons why some program components are successful and others are not, identify potential program improvements, and examine a program's cost-effectiveness. Evaluators gather information that describes how a program was conceptualized, designed, and implemented and they examine the success of the program in meeting its expected outcomes. Evaluation can be conducted by the program's staff, by an outside evaluator, or by a combination of both.