Internal Consistency Reliability

 
Reliability refers to the ability of a questionnaire to measure accurately. Internal consistency reliability (Marshall & Hales, 1972) is determined by checking the components of a questionnaire against each other. Internal consistency reliability in the form of Cronbach's Alpha is the type reported in this document.

Internal consistency reliabilities vary from a low of 0 to a high of 1.0 and represent the proportion of the variance in the respondents' scores that are attributable to true differences on the psychological construct (DeVellis, 1991). The following guidelines have been proposed by DeVellis regarding acceptable reliabilities for research instrument scales:

(DeVellis, 1991, p.85).