Internal consistency estimates of reliability


  • Dr. Sandra Ferketich

    Corresponding author
    • College of Nursing, University of Arizona, Tucson, AZ 85721
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    • Sandra Ferketich, PhD, RN, FAAN, is an associate professor and the director of Family and Community Health Nursing at the College of Nursing, University of Arizona. She also is the co-director, with Jan Atwood, PhD, RN, FAAN, of the Predoctoral and Postdoctoral Clinical Nursing Research Instrumentation Fellowship Program offered under National Research Service Award Institutional Grant No. 5T32NR07029.


Reliability assessments are appropriate for each research instrument in a study. Measures of internal consistency are a popular set of assessments with Cronbach's alpha being the most favored. Two other measures of internal consistency, theta and omega, have particular characteristics that make their use desirable under certain circumstances. Each of these three measures and its computation is described and examples provided.