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Table 2 Power of trial to detect differences across main comparisons

From: UK Back pain Exercise And Manipulation (UK BEAM) trial – national randomised trial of physical treatments for back pain in primary care: objectives, design and interventions [ISRCTN32683578]

Power to detect difference of 2.5 RMDQ points at 1% significance level

No interaction present between manipulation and exercise

Interaction present between manipulation and exercise

Analysing only completersa (no interactions present)

Exercise vs. AM only

>99%

>99%

>99%

Manipulation vs. AM only

>99%

>99%

>99%

Site of manipulationb

80%

42%

64%

Site of manipulationc

91%

66%

83%

  1. a Based on estimated completion rate of 75% b Power to detect difference of 1.67 RDQ points at 1% significance level c Power to detect difference of 1.67 RDQ points at 5% significance level