Intended for healthcare professionals

Research Methods & Reporting Statistics Notes

Brackets (parentheses) in formulas

BMJ 2011; 343 doi: https://doi.org/10.1136/bmj.d570 (Published 11 August 2011) Cite this as: BMJ 2011;343:d570

More on brackets

I would like to raise 2 further points re Bland & Altman's
article (1).

Is not the correct formula ln[p/(1-p)] ?

Then the example given comes to ln(1/4) = -ln(4).

The original formula is missing a '-' rather than brackets: it
transforms to ln[(1-p)/p]; as noted, this equates to ln(4).

It is important that this matter is cleared up before the BMJ becomes
a source of questionable formulae.

Reference
(1) Douglas G Altman and J Martin Bland

Research Methods & Reporting: Brackets (parentheses) in formulas
BMJ 2011; 343:d570

Competing interests: No competing interests

15 August 2011
Phil McShane
Statistician
University of Leeds