- Studies in which the researchers introduce the independent variable with the intent of observing the outcome, but unlike true experimental research, group selection is not randomized.
- In this study by Ghanbari et al., the independent variable was introduced by the the researchers to all individuals in the group, without randomization or a control group. Everyone was tested before treatment, received the same treatment, and was tested again after treatment.
- Ghanbari A. and Kamalgharibi S. (2013). Effect of knee joint mobilization on quadriceps muscle strength. International Journal of Health and Rehabilitation Sciences. 2(4): 186-191