1.4.1 Theory-based approaches
A theory-based (or theory-guided) approach to evaluation simply means that a theory or model has been proposed as to how a particular technology, project or programme is supposed to function and what the outcome(s) are likely to be. The examples of CCTV and Eurofighter given previously are illustrations of this type of approach. Contemporary practice in programme evaluation encourages the explicit identification and statement of the theory (or theories) that are implicit in the assumptions that underlie almost every type of project or programme. Chen (2006) differentiates between descriptive and prescriptive assumptions (or theories). I adapt his definition slightly to fit technology evaluation:
Descriptive assumptions concern the causal processes that lead to whatever problem a technology, or technology-based project or programme is aimed at addressing.
In the example of CCTV used above these would include assumptions about the causes of crime and/or why crime was particularly prevalent in some areas:
Prescriptive assumptions prescribe those entities and activities (components, resources, systems, people, etc.) that the designers and/or other key stakeholders in a technology, or technology-based project or programme deem necessary to its success.
Again, using the example of CCTV, these included prescriptive assumptions about the technology, but also about being able to position cameras in appropriate locations, and, as we saw, a range of supporting measures and activities, such as publicity.
Chen argues that taken together descriptive and prescriptive theories/assumptions provide the basis for, or guidance on, the design of an evaluation. Activity 4 provides the opportunity to work through this.
If in recent years you have been involved in evaluating a programme or related type of evaluation, you may well be familiar with a theory-based approach, as it is nowadays the preferred option of many governments, NGOs and national and international funding and development agencies (Bamberger et al., 2006). Chances are it will not have been labelled as such, but if the starting point and underpinning for the evaluation were some combination of descriptive and prescriptive theories then the evaluation was theory-based.
Activity 4 Descriptive and prescriptive theories in evaluation
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We have already explored one dimension of a theory-based approach – the nature of causal relations – through the example of CCTV. Before concluding this section I want to explore another – theories about the relationship between technology and society. These are significant for technology evaluation because of the impact they have on the descriptive and prescriptive assumptions that underlie the developments and projects we may be called on to evaluate.