  Excluding the concept of probability in quantum mechanics, we derive Born's
law from the remaining postulates in quantum mechanics using type method. We
also give a way of determining the unknown parameter in a state vector based on
an indirect measurement model. While Deutsch adopt a concept of rational
decision-maker who introduces probability, we adopt a concept of statistician
in our measurement model and clarifies the distinguished feature of quantum
measurement. Like many worlds interpretation, our scenario gives a simple
solution for problem of measurement.
