Evaluation is a systematic determination of a subject's merit, worth and significance, using criteria governed by a set of standards. It can assist an organization, program, design, project or any other intervention or initiative to assess any aim, realisable concept/proposal, or any alternative, to help in decision-making; or to ascertain the degree of achievement or value in regard to the aim and objectives and results of any such action that has been completed. The primary purpose of evaluation, in addition to gaining insight into prior or existing initiatives, is to enable reflection and assist in the identification of future change.

An alternative view is that "projects, evaluators, and other stakeholders (including funders) will all have potentially different ideas about how best to evaluate a project since each may have a different definition of 'merit'. The core of the problem is thus about defining what is of value." From this perspective, evaluation "is a contested term", as "evaluators" use the term evaluation to describe an assessment, or investigation of a program whilst others simply understand evaluation as being synonymous with applied research.

It is claimed that only a minority of evaluation reports are used by the evaluand (client) (Datta, 2006). One justification of this is that "when evaluation findings are challenged or utilization has failed, it was because stakeholders and clients found the inferences weak or the warrants unconvincing" (Fournier and Smith, 1993). Some reasons for this situation may be the failure of the evaluator to establish a set of shared aims with the evaluand, or creating overly ambitious aims, as well as failing to compromise and incorporate the cultural differences of individuals and programs within the evaluation aims and process.

Evaluating programs and projects, regarding their value and impact within the context they are implemented, can be ethically challenging. Evaluators may encounter complex, culturally specific systems resistant to external evaluation. Furthermore, the project organization or other stakeholders may be invested in a particular evaluation outcome. Finally, evaluators themselves may encounter "conflict of interest (COI)" issues, or experience interference or pressure to present findings that support a particular assessment.

Founded on another perspective of evaluation by Thomson and Hoffman in 2003, it is possible for a situation to be encountered, in which the process could not be considered advisable; for instance, in the event of a program being unpredictable, or unsound. This would include it lacking a consistent routine; or the concerned parties unable to reach an agreement regarding the purpose of the program. In addition, an influencer, or manager, refusing to incorporate relevant, important central issues within the evaluation.

House considers all major evaluation approaches to be based on a common ideology entitled liberal democracy. Important principles of this ideology include freedom of choice, the uniqueness of the individual and empirical inquiry grounded in objectivity. He also contends that they are all based on subjectivist ethics, in which ethical conduct is based on the subjective or intuitive experience of an individual or group. One form of subjectivist ethics is utilitarian, in which "the good" is determined by what maximizes a single, explicit interpretation of happiness for society as a whole. Another form of subjectivist ethics is intuitionist/pluralist, in which no single interpretation of "the good" is assumed and such interpretations need not be explicitly stated nor justified.

Stufflebeam and Webster place approaches into one of three groups, according to their orientation toward the role of values and ethical consideration. The political orientation promotes a positive or negative view of an object regardless of what its value actually is and might be-they call this pseudo-evaluation. The questions orientation includes approaches that might or might not provide answers specifically related to the value of an object-they call this quasi-evaluation. The values orientation includes approaches primarily intended to determine the value of an object´they call this true evaluation.

Politically controlled and public relations studies are based on an objectivist epistemology from an elite perspective. Although both of these approaches seek to misrepresent value interpretations about an object, they function differently from each other. Information obtained through politically controlled studies is released or withheld to meet the special interests of the holder, whereas public relations information creates a positive image of an object regardless of the actual situation. Despite the application of both studies in real scenarios, neither of these approaches is acceptable evaluation practice.

As a group, these five approaches represent a highly respected collection of disciplined inquiry approaches. They are considered quasi-evaluation approaches because particular studies legitimately can focus only on questions of knowledge without addressing any questions of value. Such studies are, by definition, not evaluations. These approaches can produce characterizations without producing appraisals, although specific studies can produce both. Each of these approaches serves its intended purpose well. They are discussed roughly in order of the extent to which they approach the objectivist ideal.

Decision-oriented studies are designed to provide a knowledge base for making and defending decisions. This approach usually requires the close collaboration between an evaluator and decision-maker, allowing it to be susceptible to corruption and bias.

Accreditation / certification programs are based on self-study and peer review of organizations, programs, and personnel. They draw on the insights, experience, and expertise of qualified individuals who use established guidelines to determine if the applicant should be approved to perform specified functions. However, unless performance-based standards are used, attributes of applicants and the processes they perform often are overemphasized in relation to measures of outcomes or effects.