14. Sample Sizes

  1. Peter M. Fayers1,2 and
  2. David Machin3,4

Published Online: 8 MAR 2002

DOI: 10.1002/0470846283.ch14

Quality of Life: Assessment, Analysis and Interpretation

Quality of Life: Assessment, Analysis and Interpretation

How to Cite

Fayers, P. M. and Machin, D. (2000) Sample Sizes, in Quality of Life: Assessment, Analysis and Interpretation, John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/0470846283.ch14

Author Information

  1. 1

    Medical Research Council Clinical Trials Unit, London, UK

  2. 2

    Unit of Applied Clinical Research, Norwegian University of Science and Technology, Trondheim, Norway

  3. 3

    NMRC Clinical Trials & Epidemiology Research Unit, Singapore

  4. 4

    School of Health and Related Research, University of Sheffield, UK

Publication History

  1. Published Online: 8 MAR 2002
  2. Published Print: 18 APR 2000

ISBN Information

Print ISBN: 9780471968610

Online ISBN: 9780470846285



  • significance tests;
  • p-values;
  • means-paired;
  • proportions-unpaired;
  • means-unpaired;
  • proportions-paired;
  • time-to-event data;
  • equivalence studies


This chapter describes how sample sizes may be estimated for QoL studies. To obtain such sample sizes it is necessary to specify, at the planning stage of the study, the size of effect that is expected. The type of statistical tests to be used with the subsequent data needs to be stipulated, as do the significance level and power. Situations in which means, proportions, ordered categorical, and time-to-event outcomes are relevant are described. Sample size considerations are included for the difference between groups, comparison with a reference population and equivalence studies, as well as unpaired and paired situations. The consequences of comparing more than two groups or simultaneously investigating several endpoints are discussed.