Details of our sample size calculations and all assumptions have been provided previously17 but are summarized briefly. Because this was a 6-arm dosing study, the calculation of sample size was inherently more complicated. Our sample size was chosen to ensure adequate power to detect a significant difference between at least 2 of the 5 massage treatment groups (and not just adequate power to find a difference between 1 or more of the treatment groups and the control group). We powered our study for the primary binary outcome of a clinically meaningful improvement in neck-related dysfunction (≥5 points on NDI). With 34 participants per group, we have 97% power to find a significant difference between at least 2 of the 6 groups (assuming that the control group had a 7% improvement and the massage groups had an improvement of 35%–70%) and 80% power to find a significant difference between 2 active massage groups. Assuming 10% loss to follow-up, we recruited 38 participants per group, for a total sample size of 228 in the trial. What are the thoughts about the sample size of the article?
Sample Size and Power
Details of our sample size calculations and all assumptions have been provided previously17 but are summarized briefly. Because this was a 6-arm dosing study, the calculation of sample size was inherently more complicated. Our sample size was chosen to ensure adequate power to detect a significant difference between at least 2 of the 5 massage treatment groups (and not just adequate power to find a difference between 1 or more of the treatment groups and the control group). We powered our study for the primary binary outcome of a clinically meaningful improvement in neck-related dysfunction (≥5 points on NDI). With 34 participants per group, we have 97% power to find a significant difference between at least 2 of the 6 groups (assuming that the control group had a 7% improvement and the massage groups had an improvement of 35%–70%) and 80% power to find a significant difference between 2 active massage groups. Assuming 10% loss to follow-up, we recruited 38 participants per group, for a total sample size of 228 in the trial.
What are the thoughts about the sample size of the article?
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