Intended for healthcare professionals

Education And Debate Statistics Notes

Blinding in clinical trials and other studies

BMJ 2000; 321 doi: (Published 19 August 2000) Cite this as: BMJ 2000;321:504

"Triple blinding in epidemiologic studies"

Sir: I am aware of a third type of blinding (in addition to the joke that defines triple blinding as that when neither the patient, nor the observer, nor the researcher know what's going on). Some researchers go as far as requiring that the statistician is also kept blind for data analysis. Considering that proper data quality control and data management have been assured, and that statistical analysis is guided by research questions and hypotheses, this practice seems rather absurd and should be avoided.

Hector E. Velasco-Mondragon, M.D., M.Sc.
Candidate in Epidemiology

Johns Hopkins School of Hygiene and Public Health

Associate Researcher

Centro de Investigaciones en Salud Poblacional

Instituto Nacional de Salud Publica
Cuernavaca, Mor. Mexico

Competing interests: No competing interests

19 August 2000
Hector E Velasco
Associate Researcher
Instituto Nacional de Salud Publica, Mexico