Performance Rating Scales
Heap, John P., Management Services
Many work measurement techniques make use of performance rating to ensure that times calculated or derived are times for 'an average qualified worker' to carry out the work being measured. Since this average qualified worker is not actually observed, performance rating is used to modify what is observed and thus convert it to 'basic time Some measurement techniques such as pre-determined motion-time systems (PMTS) do not require the observer to rate the worker(s) being observed, but such techniques have used performance rating in the derivation of the data which is applied to the observed motion pattern. Thus performance rating is an integral part of work measurement.
Unfortunately there are a number of different performance rating systems and scales and this makes it difficult to directly compare standard times derived by different methods or in different organisations.
THE PROBLEMS OF COMPARISON OF ALTERNATIVE SYSTEMS/SCALES
Increasing globalisation of large companies means that many organisations are now using a number of different work measurement techniques in different parts of the organisation. This happens because different techniques have assumed a greater degree of usage in particular countries.
These global organisations are now looking to establish compatible (or at least comparable) time standards across the organisation to simplify planning and control processes.
The working group collected published material from across Europe on rating systems/scales. Most of the material is very old (from the 40's, 50's and 60's) and there appears to be virtually no effective research on performance rating being published at the present time.
The material referring to the comparison of different rating scales shows no evidence of empirical research-it is therefore difficult to give an authoritative comment on the use and transferability of rating scales.
The earlier material contains several discussions on alternative rating systems. Presently MTM data is based on the LMS system (first published in 1927 by Lowrey, Maynard and Stegemerten)' but most current time study based rating is carried out using 'local' (BSI, REFA, MTM) rating scales. Many of these scales are very similar although they go under different names.
The relationship between time study rating and MTM performance levels is particularly important in Sweden where all rating training is done by ensuring that 'observed ratings' are compatible with MTM. Training is done by showing observers a series of film loops which have been previously analysed using MTM-1. The observer's ratings are compared with the 'ratings' from MTM and discrepancies are pointed out. Over time, the observer is trained to rate at MTM levels.
Using an MTM equivalent rating scale does allow such cross-checking on the basis of MTM analyses and thus offers a more effective means of both training and rating checking (via rating clinics) than one of the more usual systems of comparing an observer's rating with the mean of a panel of his peers.
Each of the rating systems/scales starts from a different conceptual viewpoint. The Bedaux system (now little used) assumed that 'normal' performance was 60 'minutes of work' per hour, that 80 'minutes of work' per hour was incentive performance and that 100 was a theoretical maximum.
All work measurement systems use time units to represent work content-the quantity of work involved in carrying out a particular task, operation or job. Thus the unit, such as 'standard minute' is an expression of quantity of work, rather than of time. It only converts to an equivalent time assuming that the operator works at standard performance (on the performance rating scale used) and takes the agreed level of allowances built into the work content value.
Different rating systems claim to rate different factors--commonly these are some combination of speed, effort, skill, dexterity, consistency, conditions. …