ABSTRACT
Credibility is the evaluators first concern. It is not possible to show direct causality. This is why it is essential to build a robust chain of impact and why, also, attribution and isolation has to be carried out before any impact outcome is reported. Estimation is likely to be the least-trusted form of isolation at least until people have seen it done well. The Organisation for Economic Co-operation and Development (OECD) defines attribution as the ascription of a causal link between observed changes and a specific intervention. The chapter describes regression analysis is a statistical technique for estimating the relationship between variables. The authors purpose has to be that their stakeholders and readers will be sufficiently confident of the claims people report that they will be prepared to commit to further action based on them. The Statistical Education through Problem Solving (STEPS) website defines the term time series as a sequence of observations which are ordered in time.
