Introduction Outcome evaluations designs aim to find out the effects of an interven­ tion. These designs answer the question 'Does it work?' or 'Does it work better than the alternative?' They do this by comparing the target people or organisations before and after the intervention; for example, by comparing patients' states before and after receiving a service or by comparing the health of a population before and after a health pro­ gramme or change is introduced. Some may also try to find out if the intervention makes a difference to people other than the targets. For example, what effect does it have on health personnel or patients' carers? The type 6 designs use the before-and-after design to look at the effects of an intervention to an organisation, such as a training programme or a health reform.