2. Definitions
Work study is a generic term for those techniques particularly ‘Method
Study’ and ‘Work Measurement’ which are used in the examination of
human work in all its contexts and which lead systematically to the
investigation of all the factors which effect the efficiency of the situation
being reviewed, in order to seek improvements.
3. Work Study
A method of engineering includes work simplification,
job design, value analysis and the like.
Work study comprises to two techniques known as method
study and work measurement.
https://www.youtube.com/watch?v=qUgKkBhZl9c
https://www.youtube.com/watch?v=vNfy_AHG-MU
https://www.youtube.com/watch?v=fEVdmGHDT3w
Aswathappa page 172
4. Refer Aswathappa for notes
Objectives of work study page – 172
Benefits of work study page – 173
Definitions of important terms for part A questions –
page 173
Relationship of time and motion study to work study
page – 174
Basic work study procedure – page 175-176
5. Method study
It may be defined as the systematic investigation (i.e recording and critical
examination) of the existing method of doing a job in order to develop
and install an easy, rapid, efficient, effective and less fatiguing procedure
for doing the same job and at lower costs.
6. Method study or methods
analysis
It is also known as methods improvement, work methods
analysis
It is a scientific technique for observing, recording and
critically examining the present method of performing a
task or job or operation with the aim of improving the
present method and developing a new and cheaper
method.
Page no. 176 Aswathappa
7. Refer Aswathappa for notes
page 176-180
Objectives of method study
Advantages of method study
Factor facilitating method study
Method study procedures
Recording technique used in method study
Process charts used in method study
8. Work Measurement
It is the application of different techniques to measure and establish the
time required to complete the job by a qualified worker at a defined level
of performance.
9. Work measurement
It is measuring the work content of any activity under
study.
It is the application of techniques designed to establish
the work content of specified task by determining the
time required for carrying out the task at a defined
standard of performance by a qualified worker.
10. Refer aswathappa for notes
page 183-185
Benefits of work measurement
Techniques of work measurement
Steps to work measurement
11. Advantages of Work Study
Uniform and improved production flow
Higher productive efficiency
Reduced manufacturing costs
Fast and accurate delivery dates
Better employee-employer relations
Better service to customers
Job security and job satisfaction
Better working and other conditions
Higher wages to workers
12. Advantages of Method Study
Improved working and standardized procedures.
Better work place layout
Less fatigue to operators.
Better product quality
Effective utilization of men, material & machinery
Efficient and fast material handling.
Reduced health hazards
Efficient planning of the section
Streamlined working procedures
13. Work Measurement
Determines the time required to do a job
Decides manpower to do a job
Decides equipment requirement
Provides information for effective PPC
Aids in calculating exact delivery dates
Decides realistic labor budgeting and provides a basis
for standard costing system
Provides a basis for fair and sound incentive schemes
Results in effective labor control
14. Steps in work study components
Method Study
*Select the task to be studied
*Collection, recording and presentation of facts
*Analyze the facts
*Develop the new methods
*Install the new methods
*Maintain the methods.
15. Method study
Select job/process to be examined & observe
current performance
high process cost, bottlenecks, tortuous route,
low productivity, erratic quality
Record & document facts
activities performed
operators involved - how etc
equipment and tools used
materials processed or moved
apply critical examination - challenge job
components & necessity (purpose, place,
sequence, method).
develop alternative methods & present proposals
document as base for new work system
Install, monitor (slippage) & maintain
16. Steps in work study components
Work Measurement
*Select Task to be studied
*Record the facts
*Analyze the facts
*Measure the Tasks
*Define the method and related time
*Maintain the work
17. A Time Study
select job & identify the work tasks
check the method - is it efficient/agreed?
start a Time Study sheet & break work task into "units"
several times with a stop watch & for a sample of workers, time measure
completion times for each unit of work in the job sequence
average for each worker
determine & apply worker effort rating for each worker (BSI scale)
Apply fatigue, personal & other allowances
From the observation data (worker average times) calculate standard time
for the task
Assumes: set sequence, routine work cycle (all workers), little discretion,
100% effort rating - trained/qualified, motivated/committed, working at
normal pace & not fatigued
Fix standard time and enter into measured work manual/database
19. WHAT IS WORK ENVIRONMENT
• Work environment means the milieus around a person.
It is the social and professional environment in which a
person is supposed to interact with a number of
people.
•
It is not important that an office would always be
called your work place. It can be your home
environment where you use to work for all the time
where you are supposed to interact with your family
members
20. WORK ENVIRONMENT
• A comfortable work environment should concentrate in
terms of ambience, recreational facilities, climate
control, cleanliness and fixtures.
• The interiors have been specially designed to ensure a
healthy work environment — both psychologically and
physiologically.
• The colors should be bright and attractive to create a
positive impact on the employees.
21. WORK ENVIRONMENT
people who are happy within their working
environment will work far more effectively and happily
than those who are uncomfortable.
certain aspects have to be considered for the
employees to work more effectively.
22. Noise
• Noise leads to increased levels of stress. Noise is
normally caused by loud machines and so when buying
any new plant or machinery remember to check the
noise emission levels.
• The remedies are usually quite simple i.e. providing
your employees with hearing protection, rotating the
staff who work close to noisy machinery to decrease
their exposure times, and clearly marking any 'high
noise' areas to warn people of the risk.
23. Ventilation
• Fresh air is one of the most important elements of a
working environment for several reasons:
• respiration
• the removal of excess heat
• the dilution of various airborne impurities (dust, fumes,
tobacco smoke, body odour)
• Adequate ventilation can be provided by simply allowing
windows to be opened.
24. Temperature
• The minimum temperature for sedentary work is 16
degrees Celsius (about 60 degrees Farenheit)
• work involving physical effort the minimum should be
13 degree celsius (about 55 degrees Farenheit).
• Where extreme temperatures apply i.e. work involving
furnaces or freezing compartments, employees should
be provided with the correct clothing and extra work
pauses to allow recovery.
25. Lighting
• The various reasons why lighting is important in the
workplace are:
• to illuminate potential hazards
• to prevent eye strain
• There are various other considerations such as, there
should be no glare, and there should be no sudden
contrast in levels of lighting.
• All light fittings should be kept clean and ideally the
ceiling should be light coloured to reflect the light.
26. Stress
• Stress is becoming a more and more important issue in
the world of work it can be caused by many factors
• the nature of work
• the pace of working
• payment systems
• repetition and monotony
• shift work
• the behavior of other employees
• Although different employees will react differently to
different situations so it is difficult to prevent stress
occurring.
27. Work sampling is a method of finding the percentage occurrence of a
certain activity by statistical sampling and random observations.
Work sampling is the process of making sufficient random observations of
an operator’s activities to determine the relative amount of time the
operator spends on the various activities associated with the job.
The major goal of work sampling is to determine how long, or how much
of the work day, is spent on specific types of work.
Work sampling may identify the fact that certain operators spend a large
portion of their time waiting for work, or performing paperwork tasks, or
even performing activities that are not included in their job descriptions.
One of the basic foundations of statistical sampling theory is the concept
that the larger the sample size, the results will be more accurate.
In work sampling, a sufficient number of observations must be made to be
sure that the results accurately summarize the work performed. There
are statistical formulas to help determine how many observations should
be made.
28. Advantages of Work Sampling
Can be used to measure activities that are
impractical to measure by direct observation
Multiple subjects can be included
Requires less time and lower cost than
continuous direct observation
Training requirements less than DTS or PMTS
Less tiresome and monotonous on observer
than continuous observation
Being a subject in work sampling is less
demanding than being watched continuously
for a long time
29. Disadvantages and Limitations
Not as accurate for setting time standards as other
work measurement techniques
Usually not practical to study a single subject
Work sampling provides less detailed information
about work elements than DTS or PMTS
Since work sampling deals with multiple subjects,
individual differences will be missed
Workers may be suspicious because they do not
understand the statistical basis of work sampling
30. Work Sampling
Is a statistical technique for estimating the proportion of time that
a worker or machine spends on various activities and idle time.
Used to determine: machine and personnel utilization, job
allowances and time standards.
In a work sampling study, a large number of observations are
made of the workers over an extended period of time. For
statistical accuracy, the observations must be taken at random
times during the period of study, and the period must be
representative of the types of activities performed by the subjects.
Work sampling is easier and cheaper than direct time study
because:
timing an activity
continuous observation of an activity
END 202
Work Design and Analysis
31. Work Sampling
The study of work sampling has some general characteristics
related to the work condition.
sufficient time available to perform the study: A work
sampling study usually requires a substantial period of
time to complete. There must be enough time available
(several weeks or more) to conduct the study.
multiple workers: Work sampling is commonly used to
study the activities of multiple workers rather than one
worker.
long cycle time: The job covered in the study has
relatively a long cycle time.
non-repetitive work cycles: The work is not highly
repetitive. The jobs consist of various tasks rather than a
single repetitive task.
END 202
Work Design and Analysis
32. Work Sampling Steps
Define the manufacturing tasks for which the standard time is to be
determined.
Define the task elements. These are the defined broken-down steps
of the task that will be observed during the study. Since a worker is
going to be observed, additional categories will likely be included as
well, such as "idle", "waiting for work", and "absent".
Design the study. This includes designing the forms that will be used
to record the observations, determining how many observations will
be required, deciding on the number of days or shifts to be included
in the study, scheduling the observations, and finally determining the
number of observers needed.
Make random visits to the plant and collect the observations. All
those who are affected by the study should be informed about it.
Periodically re-compute number of observations
Analyze and present the results. Prepare a report that summarizes
and analyzes all data and making recommendations when required.
END 202
Work Design and Analysis
33. Work Sampling
• Can provide information about men and machines in less time and lower
cost.
• It has three main uses:
1. Activity and delay sampling
To measure the activities and delays of workers and machines.
2. Performance sampling
To measure working time and performance index of a person on a manual
task.
3. Work measurement
To establish a time standard for a manual task.
33
34. How many observations?
• The percentage number of observations recording idle state
(worker or machine) is a reliable measure of the
percentage time that the operation is in the delay state.
• The accuracy increases as the number of observations is
increased.
Work sampling in its simplest form:
1. Make observations of one or more operators or machines at
random intervals.
2. Note if they are working or idle.
3. Give a tally mark under "working" if the operator or machine is
working and give a tally mark under "idle" if the operator or
machine is idle. 34
35. 4. Obtain the ratio of number of idle tally marks to the total
number of idle and working tally marks to calculate the
percentage of the day that the worker or machine is idle.
• Three methods could be used to obtain the sample size:
1. The formula for determining the sample size for a confidence
level of 95% (2 sigma) is:
Where S = desired relative accuracy
p = percentage expressed as a decimal (percentage occurrence of
an activity or delay being measured using a trial study)
N = number of random observations (sample size)
2. Using the alignment chart .
3. Using tables. 35
ns
observatio
of
number
Total
ns
observatio
idle
of
Number
Percentage
Idle
N
p
p
Sp
)
1
(
2
36. •After the start of the work sampling, it is advisable to
recalculate the sample size based on the current results
(calculate p based on the current results for idle and
working). This will better evaluate the progress of the study
and the resulting sample size might be lower which will save
time and cost.
Recalculation is advised at regular intervals (perhaps at the
end of each day).
•How can we determine whether the results are within the
desired accuracy after the study is completed?
This can be done in two ways:
1. First obtain percentage occurrence of an activity or
delay (p) using the results for the number of idle and
working observations and then use the above formula to
calculate S instead of N (which is already known).
36
37. 2. Using tables (see table 57).
• The resulting accuracy should be compared to the desired
accuracy.
• The result will be satisfactory if the resulting accuracy
value is lower than the desired accuracy.
• If the resulting accuracy value is higher than the desired
accuracy value, then N should be recalculated and work
sampling should be continued.
• What is the true accuracy value?
The resulting accuracy value will help us to obtain the upper
and lower value for the delay or working percentage with
a 95% confidence level.
37
38. Example:
After a work sampling study of a machine, the results
showed that the percentage time the machine was idle was
35% (p=.35, idle observations=1400, and total number of
observations=4000).
The accuracy was determined using the above formula and
was ±4.3% (S = ± 0.043). Multiply the value for S into the p
value to get the upper and lower value for the accuracy
(±4.3% X 35% = ±1.5%) and then add and subtract the
resulting value to the percentage idle time to get the upper
and lower value for the delay (1.5+35 and 35─1.5). In this
case, the true value was between 36.5% and 33.5%. This
means that we are 95% confident (we are using 2 sigma)
that the percentage idle time will be between 33.5% and
36.5%.
38
39. Control Charts
Control charts in work sampling studies enable the analyst to plot
the daily results. If a plotted point falls outside the control limits,
this is likely to indicate that some unusual or abnormal condition
may have been present during that part of the study.
In control charts, 3 sigma is usually used in determining the
upper and lower control limits. This means that there are only
three chances in 1000 that a point will fall outside the limits due
to a chance cause. It can be safely assumed that when a point
falls outside the limits, there is a reason for it.
•The formula for determining the control limits for p is:
Where n= number of daily observations= total number of
observations/number of days studied. 39
n
p
p
p
p
)
1
(
3
for
limits
Control
40. •See figure 246 as an example.
•Alignment charts could also be used to determine the upper and
lower control limits for p. See figure 247 as an example.
Use of Random Number Tables
•Work sampling requires the observations to be random, unbiased,
and independent.
• To ensure that the sample is random, random numbers tables
are used.
• The table will help to determine the time of day that an
observation should be made.
•It may also show the order in which the operators should be
observed, or the specific location in the department or plant
where a reading should be taken.
• See tables 61 and 62. 40
41. Performance Sampling
Performance sampling is simply assigning a rating of the
operator's performance or speed for each working
observation. The rating (in percent) is recorded on the
observation sheet the same as in making a time study. Each
working observation will have its own performance rating.
The performance ratings are then added up and divided by
the total number of working observations to represent the
average performance of the observed operator for the
period covered by the study.
41
42. Continuous Performance Sampling
To have a control on labor cost, time standards for specific
operations could be established (by the use of motion and
time study techniques such as MTM systems) and then a
count of the number of units finished each day could be
obtained. The actual results could be compared to time
standards to obtain a performance index for a worker or
department. This method is widely used and is very
effective in many situations. But sometimes much work
could not be measured directly, the cycles may be long and
varied, methods may not be standardized, and it is often
difficult to obtain a count of the units of completed work. In
these situations, some control of labor cost could be
achieved by the use of work sampling. Continuous
performance sampling can be performed by making
observations of all workers in a department at random
during the entire week or month and computing the results
for this period. 42
43. The process could be repeated week after week to provide
management with information related to the work force
such as:
1. Percentage of time working.
2. Percentage of time out of department.
3. Percentage of time idle.
4. Average performance index while working.
5. Labor effectiveness (item 1 x item 4).
43
44. Productivity Sampling
Performance sampling could be used to improve
productivity. Boeing has used performance sampling to
improve productivity for many years and at the present time
their program called "Productivity Sampling" covers more
than 3000 people in 120 shops. The company uses
productivity sampling to increase productivity and reduce
costs in the shops. Areas in need of improvements are
pinpointed and specific problems are revealed by the use of
productivity sampling. See figure 250 and pages 434 and 435
(Motion and time study design and measurement of work by
Barnes) for more details of the Boeing program.
44
45. Work Sampling in Non-manufacturing Activities
Work sampling is used in non-manufacturing environments
such as banks, restaurants, hospitals and department
stores to determine daily and hourly personnel
requirements and for cost control. Large companies
usually make work sampling studies of the activities of
personnel in many departments.
Determining Time Standards by Work Sampling
• In short-cycle repetitive work situations; time study,
standard data, or predetermined time data such as MTM
systems are usually preferred for establishing time
standards. But long-cycle operations and group work
could benefit more from work sampling studies in
determining time standards. 45
46. The steps for determining standard time using work sampling are
as follows:
1. Obtain the percentage of the day that the operator is working.
2. Determine the average performance index for the operator
during the working portion.
3. Determine the total working time during the day of the study.
4. Determine the number of finished pieces during the day of the
study.
5. Multiply items 1, 2 and 3 together.
6. Divide item 5 by item 4.
7. Add the allowances.
See figure 251 as an example.
Work sampling could also be used to obtain the time standard
of a group of operators performing a manual assembly task.
See figures 252 and 253 as an example. 46
