When we make a set of measurements, it is instinctive to try to correlate the observations with other results. One or more motives may be involved in this instinct: for instance, we might wish (1) to check that the measurements of other observers are reasonable, (2) to check that our measurements are reasonable, (3) to test a hypothesis, perhaps one for which the observations were explicitly made, or (4) in the absence of any hypothesis, any knowledge, or anything better to do with the data, to find if they are correlated with other results in the hope of discovering some ``new and universal truth''.