Could you please explain Stratification to me in layman's terms and then read the attached article and detail how it was used therein?
Lipchik, G. L., Nicholson, R. A., & Penzien, D. B. (2005). Allocation of patients to conditions in headache clinical trials: randomization, stratification, and treatment matching. Headache: The Journal of Head and Face Pain, 45(5), 419-428.
Stratification means dividing into different layers or strata or groups.
The stratification can be like severity of disease, patient's age and sex, etc.
As per the paper following is the key part about stratification:
Stratification is an advanced step in a systematic program of research investigating the efficacy and effectiveness of an intervention. If the trial has less than 100 per arm and there is a known prognostic (indication) factor, stratification is the best choice to ensure equal allocation across groups.
Authors emphasise why stratification needed:
While investigating prognostic factors, it's good to stratify to overcome of failure due randomization.
Hence, such stratification is useful to avoid failure chances.
The authors have described ...
Stratification is described in brief.