LAUSR

In human physiology research, response variance is often anticipated and addressed in sample size planning. This planned approach is intended to provide due consideration of variation when seeking to detect a targeted net mean effect with reasonable precision. Although this form of planning often results in dichotomous findings (i.e., significant, non-significant), rarely do ‘non-significant’ findings completely rule out meaningful effects. Given current recommendations by many journals to present individual data and increasing initiatives on precision health (Atkinson&Batterham, 2015; Booth & Laye, 2010; Ross et al., 2019), researchers are increasingly interested in differences in response variance, in addition to the net mean treatment effect. This form of secondary analysis can involve identifying variables that predict responders (individuals for whom an intervention is beneficial) versus non-responders (those for whom an intervention has nobenefit). As elegantly articulatedby IslamandGurd in their recently published article entitled, ‘Exercise response variability: Random error or true differences in exercise response?’ (Islam & Gurd, 2020), an important consideration here is whether such heterogeneity in response to an intervention is attributed to: (i) a differential, but inherent, physiological response (one that is reproducible) among individuals; or (ii) the influence of random error (i.e., noise attributable to technical and/or biological sources). In such instances, close attention should also be paid to the statistical approach adopted for such secondary analysis, as elaborated below.