Gribbin (1990: 173-4):
[Feynman explains:] In quantum mechanics, an "event" is a set of initial and final conditions, no more and no less. An electron leaves the gun on one side of our apparatus, and the electron arrives at a particular detector on the other side of the holes. That is an event. The probability of an event is given by the square of a number which is, essentially, Schrödinger's wave function, ψ. If there is more than one way in which the event can occur (both holes are open inside the experiment), then the probability of each possible event (the probability of the electron arriving at each chosen detector) is given by the square of the sum of the ψ's, and there is interference. But when we make an observation to find out which of the alternative possibilities actually happens (look to see which hole the electron goes through) the probability distribution is just the sum of the squares of the ψ's, and the interference term disappears — the wave function collapses.
From the perspective of Systemic Functional Linguistic theory, an event is a construal of experience as meaning. The probability of an event is the construal of experience as potential. The observation of an event is the construal of experience as instance.
The interference pattern that builds up on the detector screen, when there is more than one way that the event can occur, is the construal of the statistical distribution of instances in line with the potential probabilities of the system.
When experience is construed as instances of an electron going through one of the slits, the probability of the system potential is changed, and the statistical distribution of instances reflects this.
Each collapse of the wave function is the construal of experience as one instance of the overall range of system potential.