Summative evaluation looks at the impact of an intervention on the target group. This type of evaluation is arguably what is considered most often as 'evaluation' by project staff and funding bodies- that is, finding out what the project achieved.

Summative evaluation can take place during the project implementation, but is most often undertaken at the end of a project. As such, summative evaluation can also be referred to as ex-post evaluation (meaning after the event).

Summative evaluation is often associated with more objective, quantitative methods of data collection.  Summative evaluation is linked to the evaluation drivers of accountability.  It is recommended to use a balance of both quantitative and qualitative methods in order to get a better understanding of what your project has achieved, and how or why this has occurred. Using qualitative methods of data collection can also provide a good insight into unintended consequences and lessons for improvement.

Summative evaluation is outcome-focused more than process focussed. It is important to distinguish outcome from output. Summative evaluation is not about stating that three workshops were held, with a total of fifty people attending (outputs), but rather the result of these workshops, such as increased knowledge or increased uptake of rainwater tanks (outcomes).

Why undertake a summative evalation?

Here are some key reasons why you should undertake a summative evaluation:

• Summative evaluation provides a means to find out whether your project has reached its goals/objectives/outcomes.
• Summative evaluation allows you to quantify the changes in resource use attributable to your project so that you can track how you are the impact of your project.
• Summative evaluation allows you to compare the impact of different projects and make results-based decisions on future spending allocations (taking into account unintended consequences ).
• Summative evaluation allows you to develop a better understanding of the process of change, and finding out what works, what doesn’t, and why. This allows you to gather the knowledge to learn and improve future project designs and implementation.

Categories of summative evaluation

Some types of summative evaluation require the collection of baseline data in order to provide a before and after intervention figures. As such, it is important to factor this into the evaluation design.

It is considered good evaluation practice to include both formative and summative evaluation.