Pre-post study
Short definition
A pre-post study is a study in which an outcome is measured in the same people before and after an intervention, without a control group, and the difference is compared.
In plain language
It is simple and inexpensive, so it is common in early studies: for example, measuring service users' anxiety before and after a virtual reality session. The limitation is that, without a control group, it is impossible to know whether the change is due to the intervention or to other factors, such as the passing of time, the attention received or regression to the mean. The results should be read as indications, not as proof of effect.