Cronbach's alpha is a statistic that measures the internal consistency among a set of survey items that (a) a researcher believes all measure the same construct, (b) are therefore correlated with each other, and (c) thus could be formed into some type of scale. It belongs to a wide range of reliability measures.

A reliability measure essentially tells the researcher whether a respondent would provide the same score on a variable if that variable were to be administered again (and again) to the same respondent. In survey research, the possibility of administering a certain scale twice to the same sample of respondents is quite small for many reasons: costs, timing of the research, reactivity of the cases, and so on. An alternative approach is to measure ...