In the real world, there are many factors that can influence the sequence of tests, such as the length of the delay and the probability that the delayed test will be needed. When we ignore these many factors and pay attention only to the simplified model presented here, it makes sense to do all of the desired immediate tests before we do any of the desired delayed tests. We do not know to what extent this actually occurs in the real world. One complication is that medical doctors in most industrialized countries are not directly affected by the cost of the tests they select. In fact, fear of law suits gives them incentive to order unnecessary tests.