performance i. Elemental breakdown j. Definition of break points k. Recording media One of the most critical requirements for time study is that of elemental breakdown. There are some general rules concerning the way in which a job should be broken down into elements. They include the following. Elements should be easily identifiable, with definite beginnings and endings so that, once established, they can be repeatedly recognised. These points are known as the break points and should be clearly described on the study sheet. Elements should be as short as can be conveniently timed by the observer. As far as possible, elements – particularly manual ones – should be chosen so that they represent naturally unified and distinct segments of the operation. Performance rating Time Study is based on a record of observed times for doing a job together with an assessment by the observer of the speed and effectiveness of the worker in relation to the observer's concept of Standard Rating. This assessment is known as rating, the definition being given in BS 3138 (1979): The numerical value or symbol used to denote a rate of working. Standard rating is also defined (in this British Standard BS3138) as: "The rating corresponding to the average rate at which qualified workers will naturally work, provided that they adhere to the specified method and that they are motivated to apply themselves to their work. If the standard rating is consistently maintained and the appropriate relaxation is taken, a qualified worker will achieve standard performance over the working day or shift." Industrial engineers use a variety of rating scales, and one which has achieved wide use is the British Standards Rating Scale which is a scale where 0 corresponds to no activity and 100 corresponds to standard rating. Rating should be expressed as 'X' BS. Below is an illustration of the Standard Scale: Rating walking pace 0 no activity 50 very slow 75 steady 100 brisk (standard rating) 125 very fast 150 exceptionally fast The basic time for a task, or element, is the time for carrying out an element of work or an operation at standard rating. Basic time = observed time x observed rating The result is expressed in basic minutes – BMs. The work content of a job or operation is defined as: basic time + relaxation allowance + any allowance for additional work – e.g. that part of contingency