Which Measure Should be Used for Testing in a Paired Design: Simple Difference, Percent Change, or Symmetrized Percent Change?

Ankarali H., Ankarali S.

COMMUNICATIONS IN STATISTICS-SIMULATION AND COMPUTATION, vol.38, no.2, pp.402-415, 2009 (Peer-Reviewed Journal) identifier

  • Publication Type: Article / Article
  • Volume: 38 Issue: 2
  • Publication Date: 2009
  • Doi Number: 10.1080/03610910802506648
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.402-415


We aimed to determine the most proper change measure among simple difference, percent, or symmetrized percent changes in simple paired designs. For this purpose, we devised a computer simulation program. Since distributions of percent and symmetrized percent change values are skewed and bimodal, paired t-test did not give good results according to Type I error and the test power. To be to able use percent change or symmetrized percent change as change measure, either the distribution of test statistics should be transformed to a known theoretical distribution by transformation methods or a new test statistic for these values should be developed.