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Part Two
Design
Work measurement in job design
Basic times
Basic time
Terminology is important in work measurement. When a qualified worker is working on a
specified job at standard performance, the time he or she takes to perform the job is called the
basic time for the job. Basic times are useful because they are the ‘building blocks’ of time
estimation. With the basic times for a range of different tasks, an operations manager can
construct a time estimate for any longer activity which is made up of the tasks. The best-known
technique for establishing basic times is probably time study.
Time study
Time study
Rating
Time study is, ‘a work measurement technique for recording the times and rate of working
for the elements of a specified job, carried out under specified conditions, and for analysing
the data so as to obtain the time necessary for the carrying out of the job at a defined level
of performance’. The technique takes three steps to derive the basic times for the elements of
the job:
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observing and measuring the time taken to perform each element of the job;
adjusting, or ‘normalizing’, each observed time;
averaging the adjusted times to derive the basic time for the element.
Step 1 – Observing, measuring and rating
A job is observed through several cycles. Each time an element is performed, it is timed using
a stopwatch. Simultaneously with the observation of time, a rating of the perceived performance
of the person doing the job is recorded. Rating is, ‘the process of assessing the worker’s
rate of working relative to the observer’s concept of the rate corresponding to standard
performance. The observer may take into account, separately or in combination, one or
more factors necessary to carrying out the job, such as speed of movement, effort, dexterity,
consistency, etc.’ There are several ways of recording the observer’s rating. The most common
is on a scale which uses a rating of 100 to represent standard performance. If an observer rates
a particular observation of the time to perform an element at 100, the time observed is the
actual time which anyone working at standard performance would take.
Step 2 – Adjusting the observed times
The adjustment to normalize the observed time is:
where standard rating is 100 on the common rating scale we are using here. For example, if
the observed time is 0.71 minute and the observed rating is 90, then:
Basic time =
observed rating
standard rating
0.71 × 90
100
= 0.64 min
Step 3 – Average the basic times
In spite of the adjustments made to the observed times through the rating mechanism,
each separately calculated basic time will not be the same. This is not necessarily a function
of inaccurate rating, or even the vagueness of the rating procedure itself; it is a natural
phenomenon of the time taken to perform tasks. Any human activity cannot be repeated in
exactly the same time on every occasion.