Reliability and Measurement Error in the Presence of Homogeneity

This post-peer-review, pre-copyedit version of the article submitted to IUPUI ScholarWorks as part of the OASIS Project. Article reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Permission granted through posted policies on copyright owner’s website or through direct contact with copyright owner.This paper describes a limitation of using Cronbach's Alpha to estimate reliability when using a sample with homogeneous responses in the measured construct. More specifically, it describes the risk of falsely concluding that a new instrument may have poor reliability and demonstrates the use of an alternate statistic that may serve as a cushion against such errors. Data from two validation studies are used to illustrate the utility of the new statistic, referred to as R-Alpha or Relative Alpha. Included is a discussion of the limitations and appropriate use of the statistic in validating multi-item tests, assessment scales, and inventories