cronbach_alpha

Calculate Cronbach's alpha for a numeric matrix of raw scores with a row for each subject and a column for each item (e.g. question).
This could also work for dichotomous (0's and 1's) or Likert scale questionnaires. Cronbach's alpha is an index of internal consistency meaning that questionnaire items are likely measuring the same. Cronbach's alpha >=0.80 is considered good. Note that alpha can sometimes be negative. This could happen if you have items that should have been reversed scored.