Evaluation is the general term given to the assessment of whether something has achieved its intended goals or outcomes. More fully, it is the systematic, rigorous and careful application of scientific methods to assess the design, implementation or outcomes of a programme, service or other defined endeavour. Organisations providing health services or public health programmes, funders and recipients all usually have an interest in knowing whether services are safe, effective and cost-effective.
Although it is sometimes seen as distinct from research, in practice some forms of research are also evaluation and vice versa. This includes the main epidemiological study designs that aim to assess the effectiveness of treatments or programmes, such as randomised controlled trials. Furthermore, the principles of good evaluation are virtually indistinguishable from those of good research.
There are several main types of evaluation. Outcome or effectiveness evaluation aims to assess whether a programme is effective, economic evaluations consider whether a programme is cost-effective (see Chapter 37), and process evaluations assess whether the components of a programme function as expected and how they yield observed outcomes.
Evaluation is most effective when carried out prospectively; that is, evaluation is built into a programme or service from the outset, thus ensuring that relevant data are collected consistently throughout (including, preferably, before its introduction). Experimental evaluations – where some patients or areas are allocated to receive the intervention, and some not – can only be conducted prospectively. Retrospective evaluation can prove limited because there may be no clear aims and objectives or other criteria that a new programme or service was intended to meet.
Almost any activity, organisation or project can be evaluated against reasonable and measurable criteria that relate to its aims. However, in healthcare a number of valued objectives have come to dominate (Figure 43a).