The main objective of work sampling is to determine productivity by estimating the time spent on activities performed during working hours. After the percentage for each activity is calculated1, an inference is made regarding the overall time spent on each activity. This is considered to be an approximation, because work sampling cannot determine the duration of a task because it can only catch anactivity snapshot in time. Work Sampling is a fact finding tool, based on laws of probabilities,destined to reduce the amount of time needed to observe activities, tasks or events, both on machine and people level, that occur or not in a systematic manner without loss of information. When defining the analysis scope,researchers advise to use grouped categories of activities instead of building extensive lists. This is due to the fact that the number of observations needed is calculated based on the percentage of the activity that is targeted to be reduced or increased. The smaller the proportion of the activity in question, the bigger the sample size needed for gaining statistical reliability. The most common grouping used in work sampling surveys classifies activities into the following two categories:

