Born rule: P(x) = |ψ(x)|² — the probability of finding a particle at position x equals the squared amplitude of the wavefunction.
Each measurement collapses ψ to a definite position, sampled from |ψ|². After many measurements, the histogram converges to |ψ|².
The deviation between empirical frequencies and |ψ|² decreases as 1/√N (central limit theorem).