For a matrix $M$ in which entries $m_{a,b}$ denote the number of co-occurrences between elements $a,b$ from two distinct sets $A$ and $B$, how do I identify pairs with a significantly high co-occurrence? The absolute number of occurrences differs a lot between different $a$ as well as between different $b$.
If I look for entries with high $p(a|b) = m_{a,b}/|m_b|$ with $|m_{.,b}|$ being the sum of all entries $m_{.,b}$, frequently occurring $a$s are favoured, and vice versa when only considering $p(b|a)$.
So far, my approach has been to compute $p(a|b) p(b|a)$, but I lose any intuition about what the resulting number really means, and I'm wondering whether there might be a better approach.
