Null/No Information Rate (NIR): a statistical test to assess if a
  classification accuracy is significant for a given problem
Manuele Bicego Antonella Mensi
In many research contexts, especially in the biomedical field, after studying
and developing a classification system a natural question arises: "Is this
accuracy enough high?", or better, "Can we say, with a statistically
significant confidence, that our classification system is able to solve the
problem"? To answer to this question, we can use the statistical test described
in this paper, which is referred in some cases as NIR (No Information Rate or
Null Information Rate).