That is, if we are examining a phrase like the east end, the conditional probability of east given [__ end] or of end given [__ east] may be relatively low (since other words can appear in that context) and yet the phrase might still be very lexicalized if the association of both words with this context were significantly stronger than their association for other phrases.
to the extent that phrasal terms follow the regular patterns of the language, a phrase might have a relatively low conditional probability (given the wide range of alternative phrases following the same basic linguistic patterns) and thus have a low mutual expectation yet still occur far more often than one would expect from chance.