Chapter 2
Problem Solving Tools for Methods
Engineering
Our Text Book Website:

http://highered.mcgraw-hill.com/sites/0072468246/
Outline for today

A short history of Human Factors and
Ergonomics,
 Methods Engineering/Work Design
 Example of Methods Engineering
 Discussion of in-class exercise,
 Approaches for both physical and
“thinking” tasks,
A Short History
of Human Factors and Ergonomics
Year
Event
1760
Perronet makes time studies
1820
Charles W. Babbage makes time studies
1832
Charles W. Babbage publishes On the Economy of Machinery and Manufactures
1881
Frederick W. Taylor begins his time study work
1901
Gantt develops the task and bonus wage system
1910
Gilbreth publishes Motion Study
1933
First Ph.D. granted in the United State in the field of industrial engineering from
Cornell University
1949
The Ergonomics Research Society (The Ergonomics Society) founded United
Kingdom
1957
The Human Factors and Ergonomics Society is founded United States
1970
Congress passes the OSHAct, Occupational Safety and Health Administration
1981
NIOSH lifting guidelines are first introduced
1990
Americans with Disabiities Act (ADA) is passed by Congress
1995
ANSI Z-365 Standard for Control of Work-Related Cumulative Trauma Disorders
2006
50th Anniversary of the Human Factors and Ergonomics Society
Methods Engineering

Technique for:
– Increasing production per unit of time.
Example: increasing the number of customers
that can be handled per cashier by installing bar
code readers.
– Decreasing cost per unit output.
Example: decreasing total cost of each cell
phone by reducing the number of parts and thus
the labor hours required for assembly.
It is critical to look at impact on whole system.
Methods Engineering Focuses Primarily on
improving productivity though (re)design of:
Organizational
structure
Motivation:
Incentives/rewards
Work
Process
Work operations
Tools
(Products)
Work
environment
Methods Engineering

Often used synonymously with:
– Corporate re-engineering
– Work design
– Operation analysis
Big picture level
Detail level

The difference between these terms in the
level of detail.
Methods Engineering

Select project
I.D. product or service
experiencing difficulties.
 Get and present data
Study situation, take
measurements to determine
where difficulties really lie,
 Analyze the data:
Figure out which of many
problems are most critical
 Develop ideal method(s)
Identify alternative
approaches which may
address most critical
problems.




Present and install method
at the work site
Develop a job analysis
To insure operators are
adequately selected, trained,
rewarded, etc.
Establish time standards
Establish fair and equitable
standards for work
performance.
Follow up the method
Take measurements to
determine if changes really did
improve situation as predicted.
Example:
Mission Planning and control for the
Mars Exploration Rover

Researchers introduced
automated planning tool,
MAPGEN
 Tool had to fit with users’
existing way of thinking about
plans,
 Introduction of new tools caused
the planning process to change,
 Product and processes were
evolved together, over time.
Many methods can be used in many
stages of the design process
A typical spiral design process
Prototype
Testing
Requirements
Gathering
Final Performance
Evaluation or
Comparison
Design
Specification
Design
Review
Problem Solving Tools for
Methods Engineering:
help to identify what the most important
problem is

Observational tools:
– Site walk-thrus
– Observation and interviews of workers and
managers
– Ethnographic studies
Problem Solving Tools for
Methods Engineering (Ch. 2.1)

Exploratory tools
– Pareto Analysis (Vilfredo Pareto)
– Fish Diagrams (from Japan, 60’s)
– Gantt and PERT charts (40’s wartime).
Pareto Analysis

Items of interest are identified (e.g. types of
product flaws that result in scrapped parts,
time spent on each activity required to
manufacture a product or perform a service.
 Items are measured on a common scale
(such as frequency total cost, total time,
etc.)
 Items are ordered in descending order
0.00
Reasons
Had home or
family
Extended
college
Wanted to take
a lighter
Trying to get
into a major
Completed a
double major
Enjoyed
college and
Trying to
prepare for
Wanted to
work additional
1.50
Couldn't get
courses I
2.00
Wanted to take
a lighter
2.31
Had to work
more hrs to
2.50
Changed
majors after
Importance of Reason (1 - 4)
Example of a Pareto Chart
Reasons for Delay in Graduation,
All Colleges and Departments,
University of Minnesota, 2005
4.00
3.50
3.00
2.11
1.75 1.72 1.66
1.55 1.47 1.47
1.41 1.32
1.25 1.18
1.00
0.50
Example 2 Pareto chart: worker time study
Plymouth Cashier 2-2-06
Barista operations
(milk)
3.1%
Cutomer
interaction
3.0%
Personal
1.4%
Interaction with
staff
4.1%
Cashier functions
Equipment maintenance
Cleaning
6.1%
Watch door
Back to kitchen
Cleaning
Back to kitchen
7.9%
Cashier functions
48.1%
Watch door
13.1%
Equipment
maintenance
13.3%
Interaction with staff
Barista operations (milk)
Cutomer interaction
Personal
Example of a Fish Diagram
Fish Diagrams




Cause and effect diagrams
Effect is a problem = “fish head”
Causes = “fish bones”
Typical causes:
–
–
–
–
–
–
Environment
Methods
Materials
Administrative
Machine
Human
Gantt Charts

Activities shown as bars with:
– Anticipated start times
– Anticipated completion times
– Actual start and completion times

Use a vertical line to show current time
 May use color codes to show various things:
–
–
–
–
Completed activities (grey)
On going activities, on schedule (green)
Overdue activities (red)
Almost over due activities (yellow)
Example of a GANTT chart
PERT Charts:
Program Review and Evaluation Technique






Project networks
Like Gannt charts, PERT charts show activities,
start and end times
Also show variation in activity durations:
optimistic, average, pessimistic,
Show dependencies between activities,
Can identify a critical path (longest path) that
constrains minimum completion time of whole
project,
Analyze how “crashing” activities can shorten
duration of whole project.
Example of a PERT chart
Problem Solving Tools (cont.)

Recording and Analysis tools:
– Operation Process Chart
– Flow process chart
– Flow diagram
– Worker and Machine Process Charts
– Gang Process charts
– Synchronous servicing
Operation Process Charts

Chronological sequence of operations
 Show operations as a flow chart though the
worksite.
 Show the types of operations:
– Operation
– Transport
– Inspection
– Delay
– Storage
– Decision
Operation
Process
Chart:
Manufacture of
a telephone
stand
Flow Process Chart

More detail than Operation Process Chart:
 Not usually used for entire assemblies,
 Used for just one component (or operator)
 Add in information on:
– Operation duration (time to complete)
– Distance traveled (for transport operations)

Good for showing savings of a new method.
Flow
Process
Chart
Preparation of
direct mail
advertizing
Flow Diagram

Show layout of work area
 Show the flow of work through that area
 Show congestion areas, crossing worker
paths, total travel.
 Identify how layout can be redesigned to
reduce travel, motion, collisions, etc.
 Store materials near where they are used.
 Increase efficiency and safety.
Flow diagram
A revised and more efficient flow
diagram
Worker and Machine Process Chart

Show one worker, many processes
 Identify idle time for each,
 Reorganize operations to reduce idle time.
 Identify how many machines worker can
manage
Gang Process Charts

Show one machine, many workers,
 Identify idle time for each,
 Re-arrange tasks between workers to reduce
idle time.
Synchronous and Random
Servicing

Synchronous servicing: operations (usually done
by machine) take a predictable amount of time, so
the operator(s) “servicing” actions can be
synchronized with the machines’ cycle times.
 Random servicing (Asynchronous): operation
occurrences happen with some unpredictability:
e.g. machine breakages, field service calls, etc.
Synchronous Servicing
The number of
Machines an operator
Can be assigned:
n ≤ l + m
l+w
Where:
n = number of machines operator handles
l = total operator loading and unloading time
m = total machine running time
w = worker time between machines.
Example

Should n be 3 or 4?
 Figure out how much it costs per unit of
production if:
– 3 machines are assigned to each worker
– 4 machines are assigned to each worker

Choose the assignment that is least
expensive.
Random Servicing

This method applies when you have one person
handling several machines (or things) that:
– Do not run for a set length of time,
– Need servicing at irregular intervals

Examples:
– Machine repair: machines break at random times.
– Call center, calls come in at random times.
Random Servicing: Approach

The proportion of time, p, that a machine is up or
down can be estimated through a time study (Chapter
9) or a work sampling study (Chapter 14)

q=1- p

P = the probability that m out of n total machines
are down is:
P (m of n) =
n!
x pm qn-m
m! (n – m)!
Random Servicing: Example

Suppose at a call service center you have one phone
operator to answer:
– n = 4 phone lines
– p = 0.10 = probability that a phone line is in use is.
– q = 1 – p = 0.9 = the probability that a given phone line is unused,
e.g. no one on the line.

“In use” means that a caller may be either:
– waiting on the line, or
– speaking with the phone operator.

If calls come into the center at random, what is the
probability that there will be exactly three phone lines in
use? (e.g. One caller speaking with the operator, two
callers waiting).
Random Servicing: Example





4!
x (.10 ) (.94) = .66
0! (4 – 0)!
One caller
4!
x (.11 ) (.93 ) = .29
1! (4 – 1)!
Two callers
4!
x (.12 ) (.92) = .05
2! (4 – 2)!
Three callers
4!
x (.13 ) (.91) = .0036
3! (4 – 3)!
Four callers
4!
x (.14 ) (.90) = .0001
4! (4 – 4)!
No callers
Random Servicing: Example
In other words, in this situation:

Probability of exactly n calls
66 % of the time, the sales assistant
has no calls;
1
0.9
0.8

29 % of the time, exactly one call;
5 % of the time, exactly two calls,
e.g. the assistant helps one customer
while one customer waits,
0.7
Probability

0.6561
0.6
0.5
0.4
0.2916
0.3


Less than a half a percent of the
time (0.36 %), exactly three calls:
one customer is being helped while
two customers listen to Musak.
The probability that all 4 lines are in
use at once is almost non-existent.
0.2
0.0486
0.1
0.0036
0.0001
3
4
0
0
1
2
Num ber of calls
Coffee Shop Study

No studies had been done previously at this
company to assess current efficiency
 Goal: to identify any way possible of improving
productivity,
 Initial request: do a time study at 3 very
different stores, improve productivity of coffee
making process.
 Corporate goal: customer should be in and out
within 3 minutes, “door-to-door”.
Observational tools

Site walk-thrus: look at layout, tools equipment,
how they are used.
 Interviews of workers and managers to identify
what they view as problems,
 Ethnographic studies: observe work in detail as a
“fly on the wall” as it normally occurs in its
normal setting, possibly over a long period of
time. Good for observing interactions between
workers.
 Time and/or motion studies: to learn detail about
what people do and how long it takes.
Job Worksite Analysis Guide

Check list of items to think about/examine
while touring jobsite:
–
–
–
–
–
–
How do parts/products flow in and out?
What kinds of motion are involved?
Are any tools being used?
Were there awkward motions?
Is worker fatigued? Stressed?
Is there decision making?
Time and Motion studies

In a time study:
Often applied to large or
small tasks,
– Work is observed
Work is broken into
“elements”
– Each element is timed,
– The process is reengineered to be faster,
safer, less error-prone,
etc.

In a motion study:
Often applied to fine-grained
continuous motions,
– Motions are observed in
performing a task,
Motions are be divided
into “therbligs”
– The process is reengineered by:


eliminating unnecessary
motions,
re-sequencing motions.
The two are often combined.
Tools for Time and Motion
Studies

Tools can be simple and low cost:
– Stop watch,
– Pen and paper,
– Maybe a video camera. The task determines if it is
necessary.

The technique is low-tech, but can still result
in major cost savings!
How did your group speed up
your assembly process?






Use multiple packers,
Use two hands,
Lay-out pieces in advance in order of assembly,
Orient each object in correct position in advance,
Sequence objects to be easier to pack,
Fewer objects = less material handing = time
savings!
What about thinking tasks?

Time and motion studies apply to physical
aspects of the task and physical objects.

What about the psychological aspects of a
task? How can one study “thought work”
and apply factors to improve the work of
people who do: driving, design, planning,
management, and decision making?
Additional Approaches:
Time and “thought” studies


Protocol Studies
– Have the person talk out loud as they solve a problem
 E.g. create a design or manufacturing plan, or solve
an algebraic problem
– Record everything said and done on audio and video
tape, or written notes
Ethnographic Studies
– Observe in the workplace where people are doing tasks
 Nuclear power plant
 Cockpit of airplane
 NASA control center (for Mars Explorations)
– Record what is said and done (video or written notes)
– Analyze
Example of a Protocol Study
Protocol means “record”
 Need 2 volunteers

– Experimenter
– Subject

Tools:
– Normal tools used for task, often pencil and paper in an
office setting,
– Experimenter needs pencil and paper (or other
recording equipment: tape recorder, video).
A thinking task
Common themes in Human
Factors approaches

Observation of human activities in
performance of tasks,
 Re-engineer many aspects of the task (tools,
process, etc.) to improve effectiveness:
 The tools and techniques are often simple
but powerful!
In-Class Exercise

Each group will be given a set of objects to
assemble into a box.
 The items will be varied in:
– shape
– size,
– flexibility,
In-Class Exercise

Figure out how to fit all the objects in the box
– Decide what actions constitute “therbligs” or
“elements”
– Develop and record a procedure (in terms of
therbligs)

Figure out how to do it fast
–
–
–
–
Time your procedure (minutes, seconds)
Did your “therblig” descriptions change?
Did your procedure descriptions change?
Did other things change?
Rules of Exercise





Take all objects out and set them separately on
desk.
Fit all objects in the box so that you can close the
lid all the way.
No squashing or damaging objects.
You may wish to assign different roles to the
people on your team: packer, time keeper, process
recorder, observer, etc.
You will get several minutes to practice, then we
will have a competition.
Exercise (continued)

Each group please report:
– Your best time to complete the task
– Your therbligs
– Your procedure (sequence of therbligs)
– What you did to improve your time? (did you
develop new therbligs? New sequence?
Other?)
What Observational tools were
used in Coffee Shop Study?



Interviews with employees
Site walk-thru
Time studies of operations for three types of store
setups and three job roles (4 hours observation
each):
– Cashier
– Superglue
– Barista

Other measurements (had to design measurement
methods appropriate for context):
– At what rate do customers enter?
– How long does it take an individual customer to go door
to pick-up?
Site walk-thru: Customer Area
Tightly constrained workspace:
Hard to find a safe place from which to observe!
Projects
Which Exploratory Tools did we
Use in the Coffee Shop Study?

Other types of charts: rate of customer
arrival: when are the busy times?
 Comparison of total customer wait times at
different stores,
 Comparison of customer volume at different
stores,
Plymouth: Customer Arrival Rates
50
44
42
37
40
37
29
30
20
23
19
16
10
Tim e Interval
10
:0
010
:3
0
9:
30
-1
0:
00
9:
00
-9
:3
0
8:
30
-9
:0
0
8:
00
-8
:3
0
7:
30
-8
:0
0
7:
00
-7
:3
0
0
6:
30
-7
:0
0
Number of Cutsomers
2-2-06, 6:30 AM - 10:30 AM
Average total customer wait time
with minimum and maximum wait times
Total wait time (min)
All stores (each bar aggregated over 1 or more days)
0:21
0:20
0:19
0:18
0:17
0:16
0:15
0:14
0:13
0:12
0:11
0:10
0:09
0:08
0:07
0:06
0:05
0:04
0:03
0:02
0:01
0:00
0:03:44
Chanhassen 2/9/06
Volume
0:02:59
0:02:39
high
Plymouth (3 day ave.)
Store and days
high
Mounds View (2 day ave)
medium
Chanhassen (Super Automatic) Thu 2/9/06
Total wait time frequency
sample size, 84
Frequency (no. of customers experienceing
this wait)
50
45
40
35
30
27
25
22
20
20
15
8
10
4
3
5
0
0
0
0
0
0
0
0
0
0
-1
1
-2
2
-3
3
-4
4
-5
5
-6
-7
-8
-9
6
7
8
Time (Minutes)
10 -11 -12 -13 -14 -15
9
10
11
12
13
14
0
Difficult Part:

How do you translate this exploratory data
into ideas of what to do?
 What does this say about where the
problems might lie?
 How do I know if the what the data shows
is good or bad? Is the most costly item a
“problem” or a necessary part of the
process?