This paper is focused on the evaluation of the effect of influencing factors in Hand Arm Vibration Measurements. The implementation and validation of a model for a generic Hand Arm Vibration measuring process is presented and discussed. Hand Arm Vibration (hereafter referred to as HAV) measurements are nowadays largely performed either for research purposes or for hand-held tools characterization and workers’ risk assessment. The international standards coding this kind of measurement, ISO 5349s, precisely define procedures, instrumentation and data processing to be adopted. Despite the accurate definition of measurement methods, the application of these standards still leads to wide dispersion of measurement data (de Meester, 1998). This paper describes the results of an experimental campaign carried out to investigate the reasons for such dispersion. First step of the research is the implementation of an experimental campaign that allows, through statistical inference analysis, formulating a probabilistic assessment about the influence of some parameters on the measured level of vibration. The model derived from this analysis allows to evaluating quantitatively the effects of influencing factors in Hand Arm Vibration measurements. In the last part uses data obtained from a specific HAV measurement process are compared with the model prediction, showing that measurement data dispersion can be quite accurately explained considering influencing factors variability.