Work measurement is the process of establishing the time that a given task would take when performed by a qualified worker working at a defined level of performance.
There are various ways in which work may be measured and a variety of techniques have been established. The basic procedure, irrespective of the particular measurement technique being used, consists of three stages ;
The techniques used to measure work can be classified into those that rely on direct observation of the work, and those that do not. For example, some techniques, such as predetermined motion-time systems and the use of synthetic or standard data can provide times from simulation or even visualisation of the work. However, the data on which such techniques are based were almost certainly based on earlier observation of actual work.
Direct observation techniques (such as time study and analytical estimating) include a process for converting observed times to times for the "qualified worker working at a defined level of performance." The commonest of these processes is known as rating.
This involves the observer (after appropriate training) making an assessment of the worker's rate of working relative to the observer's concept of the rate corresponding to standard rating. This assessment is based on the factors involved in the work - such as effort, dexterity, speed of movement, and consistency. The assessment is made on a rating scale, of which there are three or four in common usage. Thus on the 0-100 scale, the observer makes a judgement of the worker's rate of working as a percentage of the standard rate of working (100).
The rating is then used (in a process known as "extension" in time study) to convert the observed time to the basic time using the simple formula:
Basic time = observed time x observed rating/standard rating
Rating is regarded by many as a controversial area of measurement since it is a subjective assessment. Where different observers rate differently, the resulting basic times are not comparable. However, practised rating practitioners are remarkably consistent. It is important that those undertaking the rating are properly trained, and that this training is regularly updated (to maintain a common perception of standard rating) through rating 'clinics'.
When carrying out work over a complete shift or working day, workers obviously suffer from the fatigue imposed both by the work undertaken and the conditions under which they are working. The normal practice is to make an addition to the basic time (commonly referred to as an "allowance") to allow the worker to recover from this fatigue and to attend to personal needs. The amount of the allowance depends on the nature of the work and the working environment, and is often assessed using an agreed set of guidelines and scales.
It is usual to allow some of the recovery period inherent in these allowances to be taken away from the workplace (and it is essential in adverse working conditions). Thus, work design should include the design of an effective work-rest regime.
One minority school of thought suggests that relaxation allowances are unnecessary. With work which involves, say, the carrying of heavy weights, this school suggests that the observer automatically adjusts the concept of standard rating to allow for the weight. Thus, if the standard rate of performance for walking on level ground carrying no weight is equivalent to four miles per hour, then an observer rating a worker walking while carrying a weight will not expect the equivalent rate. Thus, it is argued that the weight has been allowed for in the adjustment of standard rating and any relaxation allowance is simply a duplication of this adjustment.
In many jobs there are small amounts of work that may occur irregularly and inconsistently. It is often not economic to measure such infrequent work and an additional allowance is added to cover such work and similar irregular delays. This allowance is known as a contingency allowance and is assessed either by observation, by analysis of historical records (for such items as tool sharpening or replacement), or by experience. The end result is a standard time which includes the time the work "should" take (when carried out by a qualified worker) plus additional allocations in the form of allowances, where appropriate, to cover relaxation time, contingency time and, perhaps, unoccupied time which increases the overall work cycle (such as waiting for a machine to finish a processing cycle).
Choosing a measurement technique
The choice of a suitable measurement technique depends on a number of factors including:
To some extent there is a trade off between some of these factors. For example, techniques which derive times quickly may provide less detail and be less suitable for some purposes, such as the establishment of individual performance levels on short-cycle work.
The advantage of structured and systematic work measurement is that it gives a common currency for the evaluation and comparison of all types of work. The results obtained from work measurement are commonly used as the basis of the planning and scheduling of work, manpower planning, work balancing in team working, costing, labour performance measurement, and financial incentives. They are less commonly used as the basis of product design, methods comparison, work sequencing, and workplace design.
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