Cronbach's alpha reliability coefficient

In statistics, Cronbach’s alpha coefficient is used as an estimate of the reliability of a psychometric test. It might have calculated either for each item in the scale or an average value for all items in the scale. The reliability of the scale is accepted as good if the coefficient is found equal or greater than 0.70. On the other hand, the results should be considered whether if a low value of alpha that could be due to a low number of questions in the scale and a high value of alpha (>0.90) may suggest redundant items in the scale.