The proper segregation of sister chromatids at onset of anaphase is surveyed by the mitotic spindle assembly checkpoint. The concentration dynamics of the complexes APC:Cdc20 and MCC:APC determine exit from metaphase to anaphase. We have developed a model based on 14 proteins and complexes to describe concentration dynamics by ordinary differential equations in three compartments coupled by diffusion. One kinetochore in each compartment determines the attachment status to the spindle pole. Here, we focus on the role of noise in the segregation surveillance process. The deterministic differential equations are enriched by a stochastic term adding white noise of different amplitudes. Obviously, for the known physiological parameter ranges, noise does not disturb the checkpoint function. On the other hand, there is a connection between diffusion and noise, that could become important when considering a larger number of chromosomes.