  Commonly used evaluation measures including Recall, Precision, F-Measure and
Rand Accuracy are biased and should not be used without clear understanding of
the biases, and corresponding identification of chance or base case levels of
the statistic. Using these measures a system that performs worse in the
objective sense of Informedness, can appear to perform better under any of
these commonly used measures. We discuss several concepts and measures that
reflect the probability that prediction is informed versus chance. Informedness
and introduce Markedness as a dual measure for the probability that prediction
is marked versus chance. Finally we demonstrate elegant connections between the
concepts of Informedness, Markedness, Correlation and Significance as well as
their intuitive relationships with Recall and Precision, and outline the
extension from the dichotomous case to the general multi-class case.
