Because the colors are selected completely at random, unlike in the zener card experiments in which each symbol appears exactly five times in each test, it is particularly easy to use the binomial theorem to predict the distribution of the results. The table below shows the probability of getting N or more hits in a run of 20 trials. 5 hits is the expected number. With a little care a telepathy tester can be built which is immune to the more common experimental flaws. Unfortunately it may succeed only in demonstrating the absence of communication, not the presence of telepathy.
Negative results are also significant.