This guide, written by Howard White and Shagun Sabarwal for UNICEF, focuses on the use of modelling in impact evaluations. The paper looks at when it is appropriate to use this method and then provides step-by-step guidance on its use. It also provides some examples of models and looks at some of the ethical implications of their use.

### Excerpt

"A model is a verbal, graphic or mathematical depiction of social or economic relationships. Models provide a simplified framework by focusing on the key relationships of interest and ignoring factors considered to be more marginal. In the words of the economist Joan Robinson, “A model which took account of all the variegation of reality would be no more use than a map at the scale of one to one.”

A theory of change (see Brief No. 2, Theory of Change) is an example of a model. ‘Modelling’ as an approach to impact evaluation is usually restricted to mathematical models in economics or epidemiology, however. Mathematical models describe social and economic relationships in algebraic notation. The simplest models are single-equation models. For example, the health production function in economics expresses a health outcome, for example, infant mortality rate, as a function of income, female education, immunization, nutritional inputs and so on."

### Contents

- Modelling: a brief description
- When is it appropriate to use this method?
- How to conduct modelling
- Ethical issues and practical limitations
- Which other methods work well with this one?
- Examples of models

See more in the Impact Evaluation Series here.

### Source

Howard White and Shagun Sabarwal (2014), *Modelling, *UNICEF. Retrieved from: http://devinfolive.info/impact_evaluation/img/downloads/Modelling_ENG.pdf