Work Sampling
INSY 3021
Auburn University
Spring 2007
Work Sampling
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A technique that discovers the
proportions of total time that various
activities contribute to the job by
taking a relatively large # of
observations at random intervals
Used to determine: production
standards, machine and personnel
utilization, and job allowances.
Typically faster and cheaper than
other techniques
Advantages
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Well suited for high cycle time and
low repetition rate jobs & service
industry
Does not require the analyst to
continually observe the job
Reduced clerical time
A smaller # of hours are required to
collect the data
Operator not subjected to long
periods of observations
Advantages (con’t)
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Single analyst can study a small crew
(or # of subjects); GTT (Maynard
Handbook)
Cost of the study may be cheaper (up
to a certain # of samples)
Conducted over a long period of time
(tends to be more objective)
Study can be postponed if something
more urgent arises (no change in
study criteria)
Disadvantages
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Will not produce as good a standard as
direct time study
Cost maybe higher than suspected if
sampling rates are frequent
Subjects need to be located close
together to eliminate travel
Doesn’t provide the detailed data (C/I
ideas) that direct study does
Theory of why it works is confusing for
some people
Little bit of theory
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Based on an event being present or not.
Probability of x occurrences of an event in n
observations: (p + q)n = 1
Expand IAW binomial theorem, with the 1st term
giving the probability of x=0, the 2nd term x=1,
etc…
This distribution of probabilities is known as the
binomial distribution, with the Mean = np, and
Variance = npq.
As n becomes large, the binomial distribution
approaches the normal distribution
We’ll return to this later…
Sample Size
There are many sources of
tabulated data for determining the
# of samples required at various
confidence levels and accuracy’s.
 Formula for calculation purposes
simplifies to: n = Z2(1-P)/(P)(A2)

n=
162308
Z=
P=
A=
2.326
0.25
0.01
Confidence
99.9%
99%
95%
90%
Z
3.250
2.326
1.960
1.645
Study Plans (Protocol)
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Start with preliminary estimate of the
variable. This can be historical data,
conducting pilot study, or an educated
guess (least desirable)
Determine the desired accuracy of the
results
What level of confidence do you desire
Estimate the # of observations
Develop a sampling schedule
Design the data collection form
Determining Randomness
Random number tables
(text pg. 697)
 Random number
generators
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C++ Program
 Websites
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Random Reminder
Work Sampling Form
(Instrument)
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Forms should be custom designed to
accommodate the specific data of
interest to your study. Make the spaces
large enough to easily record the data.
Provide summary and calculations
spaces right on the form.
Commercial software available for this
application
Technique
Locate yourself at the same place
each time prior to observing the
operation
 Try to intentionally distract yourself
from the variable of observation as
you approach the site (think safety)
 Limit your time at the site to that
actually needed for the observation
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Technique (con’t)
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Try to record only the minimum data that
you will need to successfully reconstruct
the observation
Verify any discrepancy with the
supervisor or foreman
Make notes on the form after the
operator can no longer see you
Keep a pleasant attitude
Computerized Work
Sampling
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Computer and PDA programs
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Quetech Ltd, TimerPalm, UMT-Palm
Advantages
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IE time increased by a reduction in clerical
time, results realized faster
More professional appearing report
$ of performing studies is cheaper
Improved accuracy
Reduced errors by analysts
Greater use made of work sampling, because it
is less painful
Work Sampling Studies
Title
Determining staffing requirements in
institutional pharmacy
Objective
To determine if improvements can be made
to workload & staffing patterns of a satellite
pharmacy; determine the percentage of an
employee’s day which was devoted to specific
activities
Sample
1 pharmacy
Type of
sampling
Predetermined times
Length of study 3 weeks (day, evening, & night shifts)
Data Collection
Direct observation
# Observations
2400 (300 per shift)
Work Sampling Studies
Title
Task analysis of a pharmacist’s activities in a
45-bed rural hospital with comprehensive
pharmaceutical services
Objective
Determine how a pharmacist’s time was used;
calculate the portion of the work day spent in clinical
pharmacy activities; compare allocation of time in
this service with that of pharmacists in a small
hospital with product-oriented systems; investigate
potential usefulness of supportive personnel
Sample
1 pharmacy
Type of sampling
Fixed intervals – 5 minute intervals
Length of study
18 days selected randomly work days (stratified to
insure equal representation of each day) over a 6month period
Data collection
Direct observation - 5 trained observers
# Observations
1,451
Work Sampling Studies
Title
What Are the Functions of a Practicing
Pharmacist?
Objective
Detailed examination of what pharmacy
operators do with their time
Sample
20 pharmacies (stratified into 4 levels based
on prescription volume); 93 pharmacists
Type of
sampling
Fixed intervals – 3 minute intervals; stratified
based on prescription volume
Data collection
Direct observation – 1 observer
Length of study
36 hours (stratified to insure each day of week
and hour of day were adequately represented)
# Observations
14,400
Work Sampling Studies
Title
Work activities of pharmacy teams with
drug distribution and clinical
responsibilities
Objective
Evaluate pharmacists’ and technicians’ use of
time for patient care.
Sample
7 pharmacy teams (3-9 pharmacists & 1-4
technicians per team)
Type of
sampling
Random time interval (8 observations / hr /
shift)
Data collection
Self reporting
Length of study
5 months
# Observations
11,485 pharmacist observations; 7,626
technician observations
Work Sampling Studies
Title
Work Sampling: As a Win/Win
Management Tool
Objective
Detailed examination of what pharmacy
operators do with their time –seeking ways to
improve the efficiency of the operation.
Sample
Type of
Sampling
Random intervals (20-25 observations/shift)
Data Collection
Self reporting
Length of study
3 months
# Observations
2518 samples
Work Sampling Studies
Title
Work Sampling: The Application of an
Industrial Research Technique to School
Library Media Centers
Objective
Apply work sampling in a school library media
center setting
Sample
1 media center; 2 media specialists
Type of
sampling
Random time interval (4 observations per
hour)
Data collection
Self reporting
Length of study
20 days
# Observations
400
Work Sampling Studies
Title
Work Sampling: Assessing nursing
efficiency
Objective
Determine how nurses utilize their time
Sample
16 RN’s; 10-12 CNA’s; 3-4 secretaries
Type of
sampling
Predetermined times (20 minutes each shift)
Data collection
Direct observation
Length of study
24 hours (4 day shifts, 4 evening shifts, 2
night shifts on weekdays and weekends)
# Observations
2,835
Summary
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“Sell” the work sampling method
before using it
Use as large of a sample size as is
practical
Take individual observations at random
times, balance the study if necessary
Take the observations over two weeks
or more
Questions & Comments