Experiments (Experimental Studies)
Intervention/Treatment vs Control Group
- They should have similar characteristics
- Use random assignment, so that all variables will be equally present in the two groups
- Only difference should be the intervention/treatment
- Subjects should be blind (they should not know if they are in the treatment or control group)
- This is to minimise human bias
Random Assignment
- Must be random with respect to everything
- e.g. choosing people with names starting with letters is not random
Single Blind vs Double Blind
- Single blind: either participants or evaluators don’t know whether they are in/evaluating the treatment or control group
- Double blind: both participants and evaluators don’t know which group they are in/evaluating
Observational Studies
- When there are ethical issues performing the experiment
- Cause and effect issue
- the study can only show an association between two things
- it cannot provide evidence for cause and effect
- Randomisation is lost
- Participants assign themselves to the groups (they report their own data)