Data from two groups should not have been combined in analysisBMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7048.43a (Published 06 July 1996) Cite this as: BMJ 1996;313:43
- A J P Eccersley
- Lecturer Academic Surgical Unit, Royal London Hospital, London E1 1BB
EDITOR,—The quality of sperm may well be deteriorating. Unfortunately, the paper by Stewart Irvine and colleagues does not prove this, because the authors collected data from at least two separate subpopulations and combined them for analysis.1 One subpopulation was drawn from men …
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