Experimental study designs;
- Best to prove cause of diseases in Health research
- Comparative experiment ( one or more groups) with specific interventions
non exposed/placebo – exposed/intervention
- large number of each group, inclusion/exclusion criteria for identify the target population, randomly allocated
- must have ethical and ‘informed consent’
- specified period of time under strict conditions
*Careful: sample selection bias, allocation process, baseline differences, confounding, contamination the statistical analysis procedures, ethical
Two types of comparative experiments
1. Randomized clinical trial (RCT)
2. Community intervention trial (CIT)
1. Randomized Controlled Trials (RCT) and clinical trials
1) Explanatory trials or Mechanistic trials
How does it work?
- Determine: efficacy; main aim is to identify biological, physiological mechanisms for how a treatment works.
- Take place in artificial conditions that do not represent NORMAL clinical practice. They are also undertaken by “Expert” clinicians. Carefully select patients
- Use a placebo
- They are not very generalsable to routine clinical practice.
2) Pragmatic clinical trials (PCT)( in the 1960s Schwarz and Liellouch)
- Does it work? Whom does it work? How much does it cost?
- test drugs/treatments
- Determine: Risks, benefits, costs of an intervention for understanding of effectiveness