A 16-week aerobic exercise and mindfulness-based intervention on chronic psychosocial stress: a pilot and feasibility study

Table 3 Range of sample sizes required to estimate PSS-10 effects for a confirmatory RCT comparing aerobic exercise, mindfulness, combination training, and a control arm

Population effect	Target MoE	N required per cell	N adjusted	N required per cell per trial	Feasible
δ_z
−0.60	0.30	63	89	9	Yes
−0.37	0.18	132	186	19	Yes
δ_s
0.80	0.40	59	84	9	Yes
0.70	0.35	73	103	11	Yes
0.60	0.30	96	136	14	Yes
0.50	0.25	133	188	19	Yes
0.40	0.20	202	285	29	*Yes
0.30	0.15	352	496	50	No
0.20	0.10	779	1098	110	No

δ_z = within-group (T1–T0) gain in PSS-10; δ_s = between-group differences in gain scores between different arms of a future RCT; MoE = margin-of-error (i.e., the 95% confidence interval half-width); N = number of participant; per cell = paired observations (δ_z) or observations per arm of a future RCT (δ_s), Nadjusted = N required per cell adjusted for the retention rate observed in the pilot study. Feasibility is judged against 10 repetitions of the trial over a 5-year period with a maximum of N = 20 per treatment arm across each repetition (i.e., total N = 80 per trial). Yes = trial is feasible. *Yes = trial is not feasible using accuracy in parameter estimation criteria; however, the effect is detectable with 80% power. No = trial is infeasible

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