Define Quantitative and Qualitative Evidence

What are two main types of evidence used in health research and policy?

Quantitative: Numerical or statistical information (data), which often comes from surveys, surveillance or from administration records.

Qualitative:Descriptive information, which often comes from interviews, focus groups or artistic depictions such as photographs.

Quantitative evidence provides a good overall picture of a population or geographical region. It can also often be used to measure trends over time. This type of evidence is valuable for describing who, what, where and when.

Qualitative evidence provides richer, deeper and broader information based on a few individuals or case examples. This type of evidence is valuable for describing how and why.

Different kinds of evidence have their own limitations

One of the limitations of quantitative evidence is that it is typically “cleaned up” or “smoothed out”. This is done to reduce the influence of outstanding cases, as well as to compare evidence to other places or populations. Unfortunately, this practice can result in unusual cases being hidden.

What else to look for: Look for smaller research studies that concentrate on a problem like the one you are dealing with. They may have more precise details that are similar to your situation.

Qualitative evidence is often gathered in small studies and based the experiences of a very few individuals, which means that one of its limitations is that an entire population may not be well represented.

What else to look for: Ask community members and local experts if their experience is similar to what is described in the qualitative information. Consider how much of the qualitative evidence applies in your case.

Image sources: crowd, group

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