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Table 3 Size of differences detected by sample size

From: Home-based versus hospital-based cardiac rehabilitation after myocardial infarction or revascularisation: design and rationale of the Birmingham Rehabilitation Uptake Maximisation Study (BRUM): a randomised controlled trial [ISRCTN72884263]

Endpoint Difference Assumptions Precision of estimate
    95% 99%
Mean serum cholesterol/ mMol/L 0.4 Sda = 1.3 ± 0.24 ± 0.32
Systolic blood pressure/ mmHg 6 sd = 21 ± 3.9 ± 5.1
Shuttle-walk test/10 metre shuttles 6 sd=b20 or sd = * 40 ± 3.7 ± 7.4 ± 4.9 ± 9.7
HADSc anxiety 1.5 sd = 4.5 ± 0.83 ± 1.1
HADSc depression 1.5 sd = 4.0 ± 0.74 ± 0.97
Smoking cessation 20% (Jolly [66]) 45% smokers at baseline (effective sample size approx 200) 50% give up in hospital-based group 9%, 33% 5%, 37%
  1. a Standard deviation b SD 19 reported in Keell et al [76], but this study was in 50 male patients with established left ventricular dysfunction (mean 38, range 4–102). No other selection criteria stated, but may have been relatively highly selected (apart from sex) and thus likely to be a substantial underestimate of the standard deviation for our population. Further estimates are given assuming a standard deviation for our population of 40. The true value is likely to lie somewhere between these extremes c Hospital Anxiety and Depression scale