2-11 Subgroup analyses may be misleading

Comparisons of treatments often report results for a selected group of participants in an effort to assess whether the effect of a treatment is different for different types of people (e.g. men and women or different age groups). These analyses are often poorly planned and reported. Most differential effects suggested by these ‘subgroup results’ are likely to be due to the play of chance and are unlikely to reflect true differences.

Findings based on results for subgroups of people within a treatment comparison may be misleading.