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February 18, 2008
Service Time Flowchart
This post starts a series of posts to present the use of
Statistical Thinking Tools in applying
Statistical Thinking. The Statistical Thinking Tool illustrated
by this example is a flowchart.We can have flowcharts for processes
having service time objectives as well as processesprocesses
producing a physical product. Jeffries and Sells (2004) present
this example and
describe the use of statistical tools to meet company service
time objectives. We regard theiruse of statistical tools as an
application of Statistical Thinking.
A Midwest manufacturing firm processes orders for its 6
manufacturing plants and 12warehouses. Originally, each plant and
warehouse had its own order processing service staffed
by a total of 36 customer service representatives. To improve
customer service and reduce costs,the company president directed a
team to develop a centralized customer service center located
at
corporate headquarters. The president made this decision after
the team surveyed customers and
found that they were adamant that they did not want to wait for
a customer service representativeto answer a phone call and they
were not very interested in personalized service provided by aplant
or warehouse representative.
The team established a goal where 95% of incoming calls would
wait less than 2 minutes for a
customer service representative. The team acquired an Automatic
Call Distribution (ACD)system to route customer calls to customer
service representatives. The call center would
operate from 7:00 am to 7:30 pm Central Time. The following
figure gives a flowchartspecifying the process of answering
incoming customer calls.
The team collected data giving the distributions of incoming
calls by time of day and the service
times of the customer service representatives to answer the
calls. Recording and analyzing datafor individual steps in the
process flow chart is an example of disaggregation. Classifying
and
analyzing data by a factor such as time of the day is an example
of stratification.
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The customer service center staffing levels by hour of the day
is a crucial system designparameter. Wait times will be long
without adequate staff. On two occasions in the past two
months, I have had to wait more than an hour for technical
service support personnel to answermy calls. I know that this
happens because the companies involved have allocated
inadequate
staffing to handle the incoming calls.
The team developed staffing levels throughout the day using a
simulation of the processrepresented by the figure above.
Constructing a simulation requires a flowchart. Refer to
Jeffries and Sells (2004) for additional details.
The next post will illustrate the use of a flowchart for a
process producing a physical product.
References
1. Jeffries, R. D. and P. R. Sells (2004). Managing Customer
Service Using StatisticalTools: A Case Study. Annual Quality
Congress Proceedings.
