In one sense, there seems to be a lot of variability, as any of the five markers might be the sole positive one. On the other hand, of the 32 possible patterns of positive and negative markers, only 12 were observed. These viewpoints can be reconciled by listing the results as combinations of negative results (Table 1, part [b]), and reasoning as follows. One simple form of dependence is a “negative-implies-negative” rule (ie, a single ordered list such that if there is a negative result for any marker, there is also a negative result for all markers to its left). Such a list cannot be constructed for this data set. Both BE and DE occur as combinations of negative results. Now suppose there are two ordered lists of the markers (Table 1, part [c]), that each patient has a position in both lists, and that markers to the left of the patient in either list have negative results. This pair of lists generates all except one of the observed patterns, the exception being that one patient has negative results for C and D.