Work sampling

1. MEA1404 – Industrial Engineering and Management
with Industrial Organization
Unit –III Part 3
Dr. R.SARAVANAN
Professor & Head,
Department of Industrial Engineering,
Institute of Mechanical Engineering,
Saveetha School of Engineering,
Saveetha Institute of Medical And Technical Sciences, Chennai 1

2. Unit – III Work Design & Unit IV Part-I
Topics
Completed, Ongoing & Uncovered
Introduction to work study – Method study – Time study – stopwatch time study – Standard
data - Method Time Measurement (M-T-M) – Work sampling – Ergonomics.
Topic Planned Today: Time study – Work sampling – Ergonomics. (Unit III)
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3. WORK SAMPLING
1. Work sampling was originally developed by L.H.C. Tippett in Britain in 1934 for the British
Cotton Industry Research Board.
2. Work sampling is a fact-finding tool.
3. Work sampling is defined as: "A technique in which a statistically competent number of
instantaneous observations are taken, over a period of time, of a group of machines, processes
or workers. Each observation recorded for a particular activity or delay is a measure of the
percentage of time observed by the occurrence."
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4. WORK SAMPLING – Applications
1. Activity and Delay Sampling: To measure the activities and delays of workers or machine.
e.g., the percentage of time in a day, a person is working and the percentage that a person is
not working.
2. Performance Sampling: To measure working time and non-working time of a person on a
manual work, and to establish a performance index or performance level for a person during
his working time.
3. Work Measurement: Under certain circumstances, to measure a manual task, that is, to
establish a time standard for an operation.
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5. WORK SAMPLING STUDY – Pre-
Procedure
1. Decide on the Objective of the Study: It is very important to first set the objectives of study as
the duration of the study, number of observations, the design study sheet and elemental
breakdown depends upon the objective.
2. Obtain the approval of the supervisor of the department in which work study is to be
conducted. Make sure that the operators to be studied and the other people in the department
understand the purpose of the study. Obtain their cooperation.
3. Decide Upon Work and Delay Elements: Work and delay elements represent the headings
under which the observations are to be recorded. The nature of the work and delay elements
differ from company to company depending upon the objective of the study and the work.
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6. WORK SAMPLING STUDY – Procedure
1. Decide Upon the Duration of the Study: The duration of study depends upon the objective,
number of observers, the accuracy desired and the frequency of occurrence of the activity.
2. Determine the Desired Accuracy of Results: This may be stated as the standard error of a
percentage or desired accuracy. The confidence level is also to be stated.
3. Make a preliminary estimate of percentage occurrence of the activity or delay to be measured.
4. Design the Study:
1. Determine number of observations to be made.
2. Determine number of observers needed.
3. Determine the number of days or shifts needed for the study.
4. Make the detailed plans for taking observations.
5. Design the observation form. 6

7. WORK SAMPLING STUDY – Procedure
1. Make the observations according to the plan, analyze and summarize the data.
2. Check the accuracy or precision of the data at the end of the study
3. Prepare the report and state conclusions.
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8. DESIGN OF WORK SAMPLING STUDY
1. Determination of Required Number of Observations.
2. The number of observations depends upon:
1. Activity percentage (P)
2. Limits of accuracy (A)
3. Confidence level (C)
3. Number of observations at a confidence level of 95% is given by:
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9. ADVANTAGES OF WORK SAMPLING
COMPARED TO TIME STUDY
1. Many operations or activities which are impractical or costly to measure by time study can be
measured by work sampling.
2. A simultaneous work sampling study of several operators or machines may be made by a
single observer.
3. It usually requires lesser man-hours and costs less to make a work sampling study instead of
making a continuous time study.
4. Observations may be taken over a period of days or weeks thus reducing the chances of day-
to-day variations affecting results.
5. Any interruption during study will not affect the results.
6. Work sampling measurements may be made with a pre-assigned degree of reliability. 9

10. ADVANTAGES OF WORK SAMPLING
COMPARED TO TIME STUDY
1. Work sampling studies are preferred to continuous time studies by the operators being studied.
2. A stop watch is not needed for work sampling studies
3. Work sampling studies cause less fatigue and are less tedious.
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11. DISADVANTAGES OF WORK SAMPLING
1. Work sampling is uneconomical for short cycle jobs.
2. It is also uneconomical for studying a single workman or even small group of workmen or
machines.
3. Time study permits a finer breakdown of activities and delays than is possible with work
sampling study.
4. Workman may change their normal pattern of working on seeing the observer, making the
sampling study of very little value.
5. Insufficient observations are likely to produce inaccurate results.
6. It does not normally account for speed of the operator.
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12. ERGONOMICS
1. The word Ergonomics has its origin in two Greek words Ergon meaning work and Nomos
meaning laws.
2. So, it is the study of the man in relation to his work’.
3. The word ergonomics is used commonly in Europe.
4. In USA and other countries, it is called by the name "human engineering or it is also called
human factors engineering."
5. ILO defines human engineering as-"The application of human biological sciences along with
engineering sciences to achieve optimum mutual adjustment of men and his work, the benefits
being measured in terms of human efficiency and well-being."
6. The human factors or human engineering is concerned with man machine system. 12

13. ERGONOMICS
1. Thus, another definition which highlights the man-machine system is: "The design of human
tasks, man machine system, and effective accomplishment of the job, including displays for
presenting information to human sensors, controls for human operations and complex man-
machine systems.“
2. Human engineering focuses on human beings and their interaction with products, equipment
facilities and environments used in the work.
3. Human engineering seeks to change the things people use and the environment in which they
use the things to match in a better way the capabilities, limitations and needs of people.
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14. OBJECTIVES OF ERGONOMICS
1. To enhance the efficiency and effectiveness with which the activities (work) is carried out so
as to increase the convenience of use, reduced errors and increase in productivity.
2. To enhance certain desirable human values including safety, reduced stress and fatigue and
improved quality of life.
3. Thus, in general the scope and objective of ergonomics is "designing for human use and
optimizing working and living conditions."
4. Thus, human factors (ergonomics) discover and applies information about human behavior,
abilities and limitations and other characteristics to the design of tools, machines, systems,
tasks, jobs and environment for productive, safe, comfortable and effective human use.
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15. ERGONOMICS IS MULTIDISCIPLINARY
1. The various disciplines that are going to have influence on human factors are:
1. Engineering: Design of work system suitable to worker
2. Physiology: Study of man and his working environment
3. Anatomy: Study of body dimensions and relations for work design,
4. Psychology: Study of adaptive behavior and skills of people
5. Industrial hygiene: Occupational hazards and workers health. ·
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16. ERGONOMICS, PRODUCTIVITY AND
WORKING ENVIRONMENT
1. Productivity is a powerful tool to improve the standards of living of people and to enhance the
quality of work life (QWL).
2. Ergonomics is concerned with man and his working conditions.
3. Ergonomics aims at providing comfort and improved working conditions so as to channelize
the energy, skills of the workers into constructive productive work.
4. This accounts for increased productivity, safety and reduces the, fatigue.
5. This helps to increase the plant utilization.
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17. STUDY OF HUMAN ENGINEERING AREAS
1. Anthropometry and bio mechanics
2. Control of physical work environment
3. Design of man-machine system
4. Design of controls and displays
5. Accident’s fatigue and safety
6. Work place design·
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18. MAN-MACHINE SYSTEM
1. The fundamental concept in human engineering is the system.
2. A system is composed of humans, machines and other things that work together (or interact)
to accomplish some goal which these same components could not produce independently.
3. The man-machine system is a combination of one or more human beings and one or more
physical components interacting to bring about, from given inputs, some desired output.
4. Man-machine system consists of any type of physical object, device, equipment, facility and
activities performed by man.
5. One way to characterize man-machine system is the degree of manual versus machine control.
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19. MAN-MACHINE SYSTEM
1. The man will receive certain information from the machine either from dials, displays, etc.,
designed for that purpose or by observation of machine itself.
2. He will process this information and make decisions on what action to take and manipulate
controls or attend machine in some other way so as to affect its behavior in the required
manner.
3. Environmental factors will have an influence on the working of the system.
4. The efficiency with which the man functions depend on environmental factors, on his own
characteristics such as age, motivation, training and experience as well as the efficiency with
which the machine provides the information feedback and accepts control measures.
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