As in other quasi-experiments, the

As in other quasi-experiments, the group of participants who receive the intervention is selected in a non-random way (for example according to their choosing or that of the researcher).The one-group posttest-only design is especially characterized by having:No control groupNo measurements before the interventionIt is the simplest and weakest of the quasi-experimental designs in terms of level of evidence as the measured outcome cannot be compared to a measurement before the intervention nor to a control group.So the outcome will be compared to what we assume will happen if the intervention was not implemented. This is generally based on expert knowledge and speculation.Next we will discuss cases where this design can be useful and its limitations in the study of a causal relationship between the intervention and the outcome.