On the use of Mutual Information for Testing Independence

In this paper we use a well know method in statistics, the $\delta$-method, to provide an asymptotic distribution for the Mutual Information, and construct and independence test based on it. Interesting connections are found with the likelihood ratio test and the chi-square goodness of fit test. In general, the difference between the Mutual Information evaluated at the true probabilities and at the empirical distribution, can be approximated by the sum of a normal random variable and a linear combination of chi-squares random variables. This summands are not independent, however the normal terms vanishes when testing independence, making the test statistic being asymptotically a linear combination of chi-squares. The $\delta$-method gives a general framework for computing the asymptotic distribution of other information based measures. A common difficulty is calculating the first and second-order derivatives, which is already challenging in the case of Mutual Information. However, this difficulty can be circumvallated by using advance symbolic software such as Mathematica. Finally, we explore the underlying geometry of the Mutual Information and propose other statical measures which may give competing alternatives to classical tests.