This is the twenty-fourth blog in a series of 36 blogs explaining 36 key concepts we need to be able to understand to think critically about treatment claims.
Comparisons of treatments often report results for selected groups 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.