What does it mean? Looking beyond group differences in clinical research

Excerpt

It is usual practice for scientific papers to focus on the description of groups of subjects in terms of their mean scores on a particular measure and to assess differences between these groups by comparing these means using standard statistical tests. When we read that, "compared to a control group, those with a particular disorder or problem scored significantly higher on a symptom questionnaire", or "performed less well on a particular neuropsychological task", or that "those patients treated with an active treatment had lower symptom scores at the end of the trial than those treated with a placebo", we are able to make certain assumptions about that disorder or treatment. If we are interested in the strength of an effect we will often look to the effect size for an answer. There is no doubt that incorporating information derived from such comparisons is not only appropriate but forms the basis of evidence-based clinical practice. However, sometimes it is informative to look beyond the means and consider the heterogeneity and inter-individual variability that is often seen across many levels of analysis including symptoms, cognition and more basic causal processes. …