Intraclass Correlation Coefficient: Applications to estimate the temporal stability of a measuring instrument

This article presents theoretical and practical aspects about the use of the Intraclass Correlation Coefficient (ICC); it describes its advantages with respect to the Pearson's product-moment coefficient to determine the temporal stability of the scores of a measurement instrument. This research work corresponds to a methodological article. For the application of the method, 42 university students were intentionally selected, mostly women (53.4 %), aged between 17 and 26 years. The Interpersonal Reactivity Index (IRI) was administered; after three weeks the retest was performed. The results show the versatility of the ICC to provide information regarding Pearson's r. Likewise, it was found that in all cases the Pearson r coefficient slightly overestimates the stability of the IRI scores. It is concluded that the ICC reports stable and less-biased values to determine the evidence of temporal stability of a measurement instrument.