Study design turns a causal question into a plan: state a hypothesis, assign treatments, measure an outcome, and protect randomization from mistakes. section 1.3.4
A practical design proceeds through three linked stages:
- Form a hypothesis about whether a treatment or decision changes the primary outcome. section 1.3.4
- Execute the experiment carefully, especially the randomization process, because assignment errors can produce incorrect conclusions. section 1.3.4
- Analyze responses by comparing treatment groups using the observed outcome data. section 1.3.4
Comparing treatments
A medical experiment might test whether a new treatment works at least as well as an old one. If 80% improve under the new treatment and 70% under the old, the group results provide evidence for evaluating the hypothesis. section 1.3.4






