STAT 495, Fall 2010
Homework Assignment #2
1. This problem investigates a process that should be somewhat familiar to most of you,
pizza delivery. Use the Magnificent 7 to learn more about this process and how it might
be improved.
a) Construct a logical flow chart for the pizza delivery process, starting with a person
calling the pizza place until the pizza is delivered to the home that ordered it. You
can be as detailed as you want but there is no need to go overboard. You should
include several decision boxes in your flow chart.
b) Below are data on the frequency of complaints on pizza delivery from customers.
Construct a Pareto chart from this information.
Complaint
Cold
Late
Upside down
Wrong order
Wrong size
Other
Frequency
98
54
10
21
18
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c) Most customer complaints can be related to delivery time either directly (Late) or
indirectly (Cold). Construct a Cause-and-Effect diagram where the effect is variation
in delivery time, that is, the time it takes from when the pizza is ordered until it
arrives at the customer’s house. Be sure to include main causes, e.g. material,
machine, method, people, environment, etc. as well as items under each of the main
causes.
Note: You may construct the Flow Chart, Pareto chart and Cause-and-Effect diagram by
hand or with the aid of a computer.
Over a five week period, the average delivery time, in minutes, was obtained for each
day. The data are given below.
Day
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Week 1
Time
Week 2
Time
Week 3
Time
Week 4
Time
Week 5
Time
18
19
23
20
42
37
29
20
19
18
17
40
36
34
19
19
19
20
45
41
38
20
22
21
17
41
37
35
22
20
18
21
36
34
32
d) Construct a histogram of the average delivery times. Comment on the distribution of
average delivery times.
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e) Give summary values for the center and spread of the distribution of average delivery
times.
f) Construct a run chart of the average delivery times. Comment on the run chart.
g) Use stratification to split the delivery times into two groups. Construct separate
histograms, one for each group. Give summary values for the center and spread of
the distribution of average delivery times for each group. Compare the two groups in
terms of center and spread.
h) When customers call for a pizza delivery, what should the employee answering the
phone tell them if they ask how long the delivery will take?
i) Below is a plot of average pizza delivery time versus average number of orders.
Describe the relationship between the two variables. How might this plot help in
answering a customer’s enquiry about how long the delivery will take?
j)
During the week (Monday through Thursday) the pizza place has 4 delivery drivers
(delivery drivers help out in the kitchen when they are not out driving) and an
average 48.8 orders a day. On weekends (Friday through Sunday) there are 5
delivery drivers and an average of 83.4 orders per day. Given the data on delivery
times and orders, what recommendation would you make for improving the delivery
times on weekends? Be sure to support your recommendation by referring to the
data.
2. Come up with an example of a flow chart, Pareto chart or Cause-and-Effect diagram from
work or personal experience. Make sure that the chart is not proprietary. If you can’t find
one from work or your personal experience, look in books or on the internet for an
example of one of the charts. In this latter case, be sure to include a full reference to
where you found the chart.
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