Intended for healthcare professionals

Endgames Statistical Question

One way analysis of variance

BMJ 2012; 344 doi: (Published 04 April 2012) Cite this as: BMJ 2012;344:e2427
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}

Researchers investigated current trends in the use of bariatric surgery in England. In particular, they looked at the surgical techniques used and factors that influenced postoperative outcomes. A population cohort study was performed. All NHS adult patients with a primary diagnosis of obesity who had undergone a primary elective bariatric procedure (gastric bypass, gastric banding, or sleeve gastrectomy) in England between April 2000 and March 2008 were studied. The main outcome measures included mortality at 30 days and one year after surgery, unplanned readmission to hospital within 28 days, and duration of stay in hospital.1

In total, 3649 gastric band procedures, 3191 gastric bypasses, and 113 sleeve gastrectomies were performed. Patients’ characteristics at time of surgery were compared between the procedures to establish differences that might have influenced postoperative outcome. The patient characteristics compared included age. No significant difference was reported between surgical procedures in mean age (gastric bypass 42.25 years (standard deviation 9.50), gastric banding 42.44 (9.79), sleeve gastrectomy 44.18 (8.96); one way analysis of variance P=0.364).

The researchers reported that the number of bariatric surgical procedures had increased in England in recent years. Gastric banding and gastric bypass were the most prevalent procedures, with sleeve gastrectomy first recorded in 2006. Patients selected for gastric banding had lower postoperative mortality and readmission rates plus a shorter length of stay than those selected for gastric bypass.

Which of the following statements, if any, are true for one …

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