3. Different types of study designs

3.2 Analytical Studies

b. Experimental Studies

Subjects receive an intervention. Information on its effects is collected. The reference model of the experimental study is the randomized placebo-controlled or reference-controlled clinical trial. There are several types:

  • Without a control group, also known as the crossover study:The subject is its own control.
  • With a control group:The randomized trial is the reference, since, due to randomization, the sole difference between the study group and the control group is the intervention. The patient may be aware of the intervention and not the investigator (single blind trial), or both may be unaware (double blind trial). There is also the pseudo-double blind trial, whereby both the patient and the evaluator may be unaware, the evaluator not being the same individual as the one administering treatment.