In (3.3) we were vague regarding the precise relationship between the weights in a superposition of pure states and the probability of observing each of the states in a measurement. Comparing (13) with (5), however, we see that to be consistent with the observations in our apparatus, the relationship is simply that:
The probability of obtaining a result when measuring an observable in a state composed of a superposition of pure states of the observable is proportional to the complex magnitude squared of the weight of the pure state observed.
Expressed in our concrete position-momentum example, this is
