Intended for healthcare professionals

Education And Debate


BMJ 1996; 313 doi: (Published 31 August 1996) Cite this as: BMJ 1996;313:550

Grand Rounds—Hammersmith Hospital: Tuberculous enteritis

An editorial error led to authorship of this paper being attributed to the wrong person on the front cover (27 July, pp 215-7). The author is Farah B Ahmed [not S D Taylor Robinson, who is the series editor].

Trials to assess equivalence: the importance of rigorous methods

We regret that an editorial error occurred in this article by Jones et al (6 July, p 36). In the appendix two of the formulas for power calculations had brackets in the wrong places and two had a -1 wrongly inserted. The power calculations for normally distributed data should have appeared as: Two sided case

Power = 2(Phi) (δ/(square root)s2(2/n) - z(1-(alpha))-1

One sided case

Power = (Phi) (δ/(square root)s2(2/n) - z(1-(alpha))

The power calculation for binary data, one sided case, should have appeared as:

Power = (Phi) (δ/(square root)p(100 - p) (2/n) - z1-(alpha))

In addition, in the boxed example on p 37 the Greek delta symbol ((delta)) should have appeared as a Greek sigma to give the phrase: the prior estimate of (sigma)2.