Corpora: testing association strength between elements of trigrams

[John Colby]

I would like to use likelihood ratios, as has been done in Dunning[1993]
for bigrams, to test the amount of association between the elements of
trigrams.  Dunning did this for a bigram AB by determining if the distribution
of A given that B is present is the same as A given that B is not present.

To do something similar for trigrams, is it sufficient to determine for
a trigram ABC if the distribution of A given the presence of B and C is
the same as the distribution of A given that both B and C are not present?