Yes, today it is quite clear in nl.Wikipedia. I quote and translate:
"In quantum theory, reality is approached in a fundamentally different way than in classical physics, where it is assumed that there is an observer-independent reality and that physical quantities are continuous variables, which can be measured in any combination. Measurement accuracy is a practical problem in classical physics. In quantum theory (at least in the widely accepted Copenhagen-based interpretation of Niels Bohr and Werner Heisenberg), physical quantities vary stepwise (with one quantum at a time) and there is no observer-independent reality. This second fundamental difference with classical physics makes it impossible to ignore the effects of the observation itself: the choices made by the observer in setting up his experiment, largely determine the outcome thereof. The product of the inaccuracies of the simultaneous measurements of two quantities (for example location and impulse), according to Heisenberg's uncertainty relationship, has a minimal value. If one of them has been measured with the greatest possible accuracy, then the other is inevitably undefined and indeterminable. However, this relationship itself is accurately and objectively formulated. On a macroscopic scale, the influence of quantum mechanical limitations on accuracy is usually not measurable, and quantum mechanics converts to classical physics: this is called the correspondence principle."
Moreover, quantum mechanics only makes statistical statements about a series of observations, which means that the behaviour of an individual elementary particle can only be described in terms of probability.
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