of time of a group of machines, processes or workers. Each observation records what is happening at that instant and the percentage of observations recorded for a particular activity or delay is a measure of the percentage of time during which the activity or delay occurs. The advantages of this method are that It is capable of measuring many activities that are impractical or too costly to be measured by time study. One observer can collect data concerning the simultaneous activities of a group. Activity sampling can be interrupted at any time without effect. The disadvantages are that It is quicker and cheaper to use time study on jobs of short duration. It does not provide elemental detail. The type of information provided by an activity sampling study is: The proportion of the working day during which workers or machines are producing. The proportion of the working day used up by delays. The reason for each delay must be recorded. The relative activity of different workers and machines. To determine the number of observations in a full study the following equation is used: Where: Predetermined motion time system A predetermined motion time system is a work measurement technique whereby times established for basic human motions (classified according to the nature of the motion and the conditions under which it is made) are used to build up the time for a job at a defined level of performance. The systems are based on the assumption that all manual tasks can be analysed into basic motions of the body or body members. They were compiled as a result of a very large number of studies of each movement, generally by a frame-by-frame analysis of films of a wide range of subjects, men and women, performing a wide variety of tasks. The first generation of PMT systems, MTM1, were very finely detailed, involving much analysis and producing extremely accurate results. This attention to detail was both a strength and a weakness, and for many potential applications the quantity of detailed analysis was not necessary, and prohibitively time -consuming. In these cases "second generation" techniques, such as Simplified PMTS, Master Standard Data, Primary Standard Data and MTM2, could be used with advantage, and no great loss of accuracy. For even speedier application, where some detail could be sacrificed then a "third generation" technique such as Basic Work Data or MTM3 could be used. Synthesis