  Several approaches to testing the hypothesis that two histograms are drawn
from the same distribution are investigated. We note that single-sample
continuous distribution tests may be adapted to this two-sample grouped data
situation. The difficulty of not having a fully-specified null hypothesis is an
important consideration in the general case, and care is required in estimating
probabilities with ``toy'' Monte Carlo simulations. The performance of several
common tests is compared; no single test performs best in all situations.
