10. Measurement

  1. A. Gouveia Oliveira

Published Online: 12 JUL 2013

DOI: 10.1002/9781118670767.ch10

Biostatistics Decoded

Biostatistics Decoded

How to Cite

Oliveira, A. G. (ed) (2013) Measurement, in Biostatistics Decoded, John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9781118670767.ch10

Editor Information

  1. Department of Pharmacy, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil

Publication History

  1. Published Online: 12 JUL 2013
  2. Published Print: 3 SEP 2013

ISBN Information

Print ISBN: 9781119953371

Online ISBN: 9781118670767



  • clinical questionnaires;
  • concordance;
  • factor analysis;
  • factor rotation;
  • factor scores;
  • reliability;
  • statistical method;
  • validity


There are many ways of developing clinical questionnaires but factor analysis, being a formal statistical method, deserves an explanation. This chapter discusses briefly the underpinnings of the method. It also talks about the methods of validation. There are several methods for extracting the factors, there are several methods for rotation of the factors, and there are several methods for obtaining factor scores, each method giving different results. These features of factor analysis open the door to the possibility of experimenting with several methods until the results are in agreement with the prior beliefs and expectations of the researcher. Reliability is considered a sine qua non condition for validity and therefore the first step in the evaluation of the validity of a questionnaire should be an assessment of its reliability. The chapter discusses a widely used method for the evaluation of internal consistency reliability.