Any interim analysis should be planned in advance. Consider its rationale, how the findings will be used and any implications for the ongoing programme and evaluation.
Sharing interim findings might encourage or improve evaluation engagement from service delivery providers and practitioners, for example, increasing its chances of success. Sometimes a funder or programme developer wants findings before the end of a lengthy and costly evaluation to plan for future funding or to shape the service.
Interim findings tend to be based on small amounts of data collected in a programme’s early stages. This early data may be unrepresentative of the target population and may not reveal significant results. Interim findings may also be susceptible to change and differ from final evaluation results.
As such, evaluators should consider the usefulness and implications of sharing these findings before the evaluation is finished.
In other cases, there may be a more practice-based rationale for carrying out interim analysis and reporting findings. It can help to identify difficulties, limitations or gaps in service delivery or evaluation methodology at an early stage. This allows time to make appropriate changes to a service or adapt the evaluation, including the measures being used.
Careful consideration needs to be given to making service changes part way through an evaluation: if the evaluation tests a particular way of working, what implications would a service delivery change have? This issue is most pertinent to robust evaluation designs such as randomised control trials (RCTs).