Letters

Different sex ratios at birth in Europe and North America

BMJ 2002; 325 doi: https://doi.org/10.1136/bmj.325.7359.334/a (Published 10 August 2002) Cite this as: BMJ 2002;325:334

Does it matter?

  1. Adam Jacobs, director (ajacobs@dianthus.co.uk)
  1. Dianthus Medical, London SW19 3TZ
  2. Department of Psychoanalysis and Psychotherapy, Statistics and Documentation Branch, University of Vienna Medical School, A-1090 Vienna, Austria
  3. Department of Psychology, York University, Toronto, Ontario M3J 1P3, Canada
  4. Queen's University of Belfast, Clinical Institute, Belfast BT12 6BJ
  5. 21 St Augustine Road, Penarth, South Glamorgan, Wales CF64 1BH
  6. Royal Belfast Hospital for Sick Children, Belfast BT12 6BJ
  7. Queen's University of Belfast, Clinical Institute, Belfast BT12 6BJ
  8. Belfast Link Laboratories, Royal Hospital Trust, Belfast BT12 6BE

    EDITOR—Grech et al seem to confuse statistical significance with practical significance.1 They found highly significant differences in sex ratios among the regions they studied not because of large differences in the sex ratios but because of their large sample sizes. In any case, the use of significance testing in this context is questionable: the purpose of significance testing is to make inferences about a population from a sample, and here whole populations are being studied. What is the population about which Grech et al are trying to make inferences?


    Embedded Image

    (Credit: ARMEN KACHATURIAN/PHOTONICA)

    In all regions that Grech et al studied I would expect 51 boys out of every 100 live births. Dodifferences in sex ratio at the third decimal place and beyond really have any practical significance?

    References

    Latitude has important role

    1. Martin Voracek, research resident. (martin.voracek@akh-wien.ac.at),
    2. Maryanne L Fisher, PhD candidate
    1. Dianthus Medical, London SW19 3TZ
    2. Department of Psychoanalysis and Psychotherapy, Statistics and Documentation Branch, University of Vienna Medical School, A-1090 Vienna, Austria
    3. Department of Psychology, York University, Toronto, Ontario M3J 1P3, Canada
    4. Queen's University of Belfast, Clinical Institute, Belfast BT12 6BJ
    5. 21 St Augustine Road, Penarth, South Glamorgan, Wales CF64 1BH
    6. Royal Belfast Hospital for Sick Children, Belfast BT12 6BJ
    7. Queen's University of Belfast, Clinical Institute, Belfast BT12 6BJ
    8. Belfast Link Laboratories, Royal Hospital Trust, Belfast BT12 6BE

      EDITOR—In their ecological study of 27 countries Grech et al reported a higher male to female ratio at birth for southern Europe than for central and Nordic Europe.1 A reversed latitudinal relation emerged for North America, with Mexico and the United States yielding lower sex ratios than any European country; Canada's sex ratio (although not stated) …

      View Full Text

      Sign in

      Log in through your institution

      Free trial

      Register for a free trial to thebmj.com to receive unlimited access to all content on thebmj.com for 14 days.
      Sign up for a free trial

      Subscribe