When we talk about evidence, we recommend keeping the following two types of evidence in mind (WHO 2021):
Is produced systematically through a formal, standardised research process following certain methodological standards. It can include primary research, synthesis of existing research (secondary research), and other products and guidelines based on evidence such as guidelines (tertiary research). Scientific evidence can be numerical (quantitative) or descriptive (qualitative), using a range of methodologies.
Constitutes more informal knowledge based on the opinions and experiences of people who work or live in the area being analysed. This type of evidence is often expressed in the media, expert reports, personal anecdotes, qualitative interviews, group discussions or deliberative dialogues.
Both types of evidence can be valuable and answer different research questions. Their relationship is complementary. For example, experiential research can highlight an area to focus scientific research on, or it can validate or question the scientific research already carried out.
Typical research questions that can be answered by each respective evidence type (Superu 2018):
When deciding which evidence to base decisions on, it is important to assess the robustness and quality of the available evidence. There are numerous guidelines from research associations and institutions that provide a detailed overview of quality standards for the production of evidence.
In the German market, the ‘Gesellschaft für Evaluation e.V.’ (DeGEval) provides a good overview of the standards for evaluations and ‘Arbeitskreis Deutscher Markt- und Sozialforschungsinstitute e.V.’ ADM e.V. offers a useful checklist for clients commissioning surveys. In practice, however, it is more useful to be guided by concise and clear frameworks highlighting key dimensions of good evidence, such as the following framework from evidence-based policy practice in the UK (Houses of Parliament 2017, Nesta 2022).
When trying to assess evidence from a variety of sources and methods, it is helpful to ensure that it fulfils the following criteria:
| Authoritative | It is important to assess where the information comes from and who created it. Are the qualifications of the authors credible and is their approach transparent? |
| Objective | To understand the aim behind any research and the possible biases that may occur, you should consider the purpose of the study and the likely motivations behind it. In this context, it is often useful to check who funded the research. |
| Relevant | Not all research is useful to your question or situation. You should therefore check whether the context in which the research took place is comparable to your own, whether all relevant perspectives were included, and which target group the research was originally intended for. |
| Timely | If you are basing your decision on evidence, it is important that this evidence is not out of date and is still valid. You should therefore check whether the information you have is up to date and whether anything important has happened in the meantime that could affect the results. |
| Accurate | To assess the quality of a method, you should ensure that the methodology is described in detail and is appropriate. It is also helpful to check if similar studies have been conducted or whether the study has been repeated. As a rule, peer review or validation by other experts in the field is a good sign of strong evidence. |
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