For healthcare professionals only

Endgames Statistical Question

Populations and samples

BMJ 2012; 344 doi: (Published 02 May 2012) Cite this as: BMJ 2012;344:e3048
  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 the association between use of proton pump inhibitors and risk of hip fracture in postmenopausal women. In total, 79 899 women enrolled in the Nurses’ Health Study, a prospective cohort study initiated in the United States, provided data biennially from 2000 until June 2008. The primary outcome was time until first hip fracture. The incidence rate of hip fracture was higher among regular users of proton pump inhibitors than among non-users (2.02 versus 1.51 fractures per 1000 person years).1

Which of the following statements, if any, are true?

  • a) The statistical population was the population of the United States.

  • b) The incidence rates of hip fracture among regular users and non-users of proton pump inhibitors were point estimates.

  • c) The incidence rates of hip fracture were subject to sampling error.


Statements b and c are true, while …

View Full Text

Log in

Log in through your institution


* For online subscription