We show that the mathematical formalism of the quantum statistical model can be interpreted as a method for approximation of classical (measure-theoretic) averages on the infinite-dimensional phase space. The technique of approximation is based on the Taylor expansion of functionals of classical fields. To find the order of the deviation of quantum statistical predictions from the classical predictions, we use the time-scaling arguments. We show that quantum randomness might be considered as the result of random fluctuations at the Planck time-scale.