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[Psychometric properties of a scale: internal consistency]
Adalberto Campo-Arias1, Heidi C Oviedo
1Instituto de Investigación del Comportamiento Humano, Bogotá, Colombia. campoarias@comportamientohumano.org
Abstract:
Internal consistency reliability is the degree of correlation between a scale's items. Internal consistency is calculated by Kuder-Richardson's formula 20 for dichotomous choices and Cronbach's alpha for polytomous items. 0.70 to 0.90 internal consistency is acceptable. 5-25 participants are needed for each item when computing the internal consistency of a twenty-item scale. Internal consistency varies according to population and then it is necessary to report it always that scale is used.
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