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International Journal of Public Health

, Volume 58, Issue 4, pp 637–642 | Cite as

The reliability of a two-item scale: Pearson, Cronbach, or Spearman-Brown?

  • Rob Eisinga
  • Manfred te Grotenhuis
  • Ben Pelzer
Hints & Kinks

Introduction

To obtain reliable measures researchers prefer multiple-item questionnaires rather than single-item tests. Multiple-item questionnaires may be costly however and time-consuming for participants to complete. They therefore frequently administer two-item measures, the reliability of which is commonly assessed by computing a reliability coefficient. There is some disagreement, however, what the most appropriate indicator of scale reliability is when a measure is composed of two items. The most frequently reported reliability statistic for multiple-item scales is Cronbach’s coefficient alpha and many researchers report this coefficient for their two-item measure (Cuijpers et al. 2009; Löwe et al. 2005; Michal et al. 2010; Young et al. 2009). Others however claim that coefficient alpha is inappropriate and meaningless for two-item scales (Sainfort and Booske 2000; Verhoef 2003; Cramer et al. 2006; O’Brien et al. 2008). Instead, they recommend using the Pearson correlation...

Keywords

Coefficient Alpha True Score Local Dependence Classical Test Theory True Reliability 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The authors are grateful to William Revelle and an anonymous reviewer for helpful comments on a previous version of this manuscript and suggestions for improvements.

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Copyright information

© Swiss School of Public Health 2012

Authors and Affiliations

  • Rob Eisinga
    • 1
  • Manfred te Grotenhuis
    • 1
  • Ben Pelzer
    • 1
  1. 1.Radboud University NijmegenNijmegenNetherlands

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