Principles of Experimental Design
Researchers attempt to control for differences between treatment groups.
Researchers randomize patients into treatment groups to account for variables that cannot be controlled.
The more cases we observe, the more we can estimate the effect of the explanatory variable on the response. In a single study, we replicate by collecting a sufficiently large sample. We can also replicate an entire study to verify earlier findings.
When researchers are aware of other variables (other than the explanatory variable) that may influence the result, they may first group individuals based on this variable into blocks and then randomize cases within each block. Blocking is like stratifying.
Placebos are fake treatments administered to the control group in medical studies.
Blinding is when experimental units do not know if they are in the control or treatment groups.
Double-blinding is when both experimental units and the researchers do not know who’s in the control andwho’s in the treatment group.