Pairwise comparison
Some believe that indifference (lack of preference) is not transitive.  Consider the following example.  Suppose you like apples and you prefer apples that are larger.  Now suppose there exists an apple A, an apple B, and an apple C that are the same except for the following. Suppose B is larger than A, but it is not possible to see this without an extremely sensitive measuring device.  Also suppose C is larger than B, but this also can't be seen without a sensitive measuring device.  However, the difference in sizes between apples A and C is large enough that you can see it. In psychophysical terms, the size difference between A and C is above the just noticeable difference ('jnd') while the size differences between A and B and B and C are below the jnd.