Analytical estimating is a structured work measurement technique. The formal BSI definition (22022)
states that it is
a development of estimating, in
which the time required to perform each constituent part of a task at
a defined rate of working is estimated from knowledge and practical
experience of the work and/or from synthetic data
An important feature of this technique, which helps to improve accuracy, is that a whole job should be broken down into smaller individual tasks. This is because any errors in the time estimates may be seen as random and will therefore compensate for each other.
Analytical estimating would normally be used for assessing work over a reasonably lengthy period of time, where it may be difficult and more expensive to collect the information required using other measurement techniques. Also, in some work environments the presence of an individual carrying out work measurement in the work place could be unacceptable. In these cases, analytical estimating may be an appropriate method to use, assuming someone with experience of the work is available to apply their experienced judgement. ( This may be work measurement personnel who have previous experience of this particular work )
However, the work content of some jobs cannot be estimated in advance because one is unclear about what is required until an assembly operation has been tested or stripped down. For example, during the progress of repair unforeseen and non standard difficulties can arise. Removing a wooden door from its frame by unscrewing 8 or 12 screws could take five minutes if the screws were recently inserted, or a great deal longer if the screws are rusted and clogged with paint.
In summary, the technique is used most commonly in any work environment where a lengthy time (and associated high cost) is needed to collect data.
Perhaps the most significant advantage of using anaytical estimating is its speed of application and low cost. Using trained and experienced personnel process and measurement data can be quickly assembled and applied.
However, the use of experienced judgement when determining the time necessary to perform a task is the technique's most obvious source of weakness when compared with a more precise technique such as time study. This is why the technique would not normally be used when a more precise and accurate alternative is a feasible and economic alternative, particularly to highly repetitive, standardised operations. Many jobs, such as craft work in the maintenance field, consist of a group of tasks which are periodically repeated but the precise nature of each task varies each time in minor respects ( see research on Natural & Normal Variation for further explanation). In this example, since it is impractical, in terms of time and cost, to allocate one time study observer permanently to each craftsman, the alternative is to use a time-study basis plus the experienced judgement of an ex-craft work-study observer to allow for detailed task variations.