Statistics are improbable

EDITOR—Although this paper by Pawlikowska et al is nearly six years old, I read it only two months ago.1 I am surprised that there seem to be no letters or articles referring to it to point out that the analysis is flawed.

The authors report results from a general health questionnaire on a scale of 0 to 36. They provide a histogram for the distribution, which has a mean close to 14. The authors quote the mean scores for men and women as 24.7 and 26.2 respectively. They give confidence intervals for these means and for the difference between them. These means are both above the 90th centile of the distribution of general health questionnaire score that they show. They are clearly impossible.

Their …