NotesFAQContact Us
Search Tips
Back to results
Peer reviewed Peer reviewed
Direct linkDirect link
ERIC Number: EJ968241
Record Type: Journal
Publication Date: 2012-Jun
Pages: 15
Abstractor: As Provided
ISSN: ISSN-1082-989X
Examining the Reliability of Interval Level Data Using Root Mean Square Differences and Concordance Correlation Coefficients
Barchard, Kimberly A.
Psychological Methods, v17 n2 p294-308 Jun 2012
This article introduces new statistics for evaluating score consistency. Psychologists usually use correlations to measure the degree of linear relationship between 2 sets of scores, ignoring differences in means and standard deviations. In medicine, biology, chemistry, and physics, a more stringent criterion is often used: the extent to which scores are identically equal. For each test taker (or other unit of measurement), the difference between the 2 scores is calculated. The root mean square difference (RMSD) represents the average change from 1 set of scores to the other, and the concordance correlation coefficient (CCC) rescales this coefficient to have a maximum value of 1. This article shows the relationship of the RMSD and CCC to the intraclass correlation coefficients, product-moment correlation, and standard error of measurement. Finally, this article adapts the RMSD and the CCC for linear, consistency, and absolute definitions of agreement. (Contains 3 tables and 6 footnotes.)
American Psychological Association. Journals Department, 750 First Street NE, Washington, DC 20002-4242. Tel: 800-374-2721; Tel: 202-336-5510; Fax: 202-336-5502; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A