Time study is a structured process of directly observing and measuring (using a timing device) human work in order to establish the time required for completion of the work by a qualified worker when working at a defined level of performance.

It follows the basic procedure of systematic work measurement of :

* analysis (of the work into small, easily-measurable components or elements);
* measurement (of those components); and
* synthesis (from those measured components to arrive at a time for the complete job).

The observer first undertakes preliminary observation of the work (a pilot study) to identify suitable elements which can be clearly recognised on subsequent occasions and are convenient, in terms of their length, for measurement.

Subsequent studies are taken during which the observer times each occurrence of each element (using a stopwatch or other timing device) while at the same time making an assessment of the worker's rate of working on an agreed rating scale. (One of the prime reasons for measuring elements of work, rather than the work as a whole is to facilitate the process of rating. The rate at which a worker works will vary over time; if elements are carefully selected, the rate of working should be consistent for the relatively short duration of the element. More information on rating is given within the entry on work measurement.) This assessment of rating is used to convert the observed time for the element into a basic time - a process referred to as "extension". It is essential that a time study observer has been properly trained in the technique and especially in rating.

Time study, when properly undertaken, involves the use of specific control mechanisms to ensure that timing errors are within acceptable limits. Increasingly, timing is by electronic devices rather than by mechanical stopwatch; some of these devices also assist in subsequent stages of the study by carrying out the process of "extending" or converting observed times into basic times.

The number of cycles that should be observed depends on the variability in the work and the level of accuracy required. Since time study is essentially a sampling technique in which the value of the time required for the job is based on the observed times for a sample of observations, it is possible using statistical techniques to estimate the number of observations required under specific conditions. This total number of observations should be taken over a range of conditions (where these are variable) and, where possible, on a range of workers.

Once a basic time for each element has been determined, allowances are added (for example, to allow the worker to recovere from the physical and mental effects of carrying out the work) to derive a standard time.

Time study is a very flexible technique, suitable for a wide range of work performed under a wide range of conditions, although it is difficult to time jobs with very short cycle times (of a few seconds). Because it is a direct observation technique, it takes account of specific and special conditions but it does rely on the use of the subjective process of rating. However, if properly carried out it produces consistent results and it is widely used. Additionally, the use of electronic data capture devices and personal computers for analysis makes it much more cost effective than previously.


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 ;

* an analysis phase in which the job is divided into convenient, discrete components, commonly known as elements;
* a measurement phase in which the specific measurement technique is used to establish the time required (by a qualified worker working at a defined level of performance) to complete each element of work;
* a synthesis phase in which the various elemental times are added, together with appropriate allowances (see below), to construct the standard time for the complete job.

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.

Rating

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'.

Allowances

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. The addition of allowances should never be used to compensate for an unsafe or unhealthy working environment.

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:

* the purpose of the measurement;
* the level of detail required;
* the time available for the measurement;
* the existence of available predetermined data;
* and the cost of measurement.

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.

(Kaynak : Leeds Metropolitan University)