Surface stabilized antiferroelectric liquid crystals are known to give multiplex-compatible greyscales by applying simple waveforms. Statistical variations of cell parameters are believed to be at the origin of this greyscale. In this work, an antiferroelectric model is applied to the study of cell statistical variations, aiming to identify the parameters whose variations may account for the experimental results obtained with these cells. It has been found that moderately small parameter variations, well within manufacturing tolerances, may lead to greyscales whose voltage range and shape are similar to those observed experimentally.