Cronbach’s Alpha is not a Measure of Unidimensionality or Homogeneity

Reliability is a characteristic of scores, not tests or measurement instruments. One of the methods to estimate the reliability of the scores on a test or measurement instrument is Cronbach’s coefficient alpha method. In other words, Cronbach’s alpha is an estimate of the score reliability based on the internal consistency among the [item] scores. In addition to this, Cronbach’s coefficient alpha should not be interpreted as a measure of the test’s or the measurement instrument’s unidimensionality or taken as an index of the homogeneity of a measurement instrument. Briefly, Cronbach’s alpha is not a measure of unidimensionality or homogeneity.