OSC 5100 - Final/Midterm Exam Guide Questions With
Complete Solutions
The two pictures below show us what happens when we pool
servers & when we decrease the variability.
From these pictures we can clearly see that:
Pooling servers increases the average inventory in a similar
fashion as decreasing the variability
Pooling servers reduces the average inventory in a similar
fashion as increasing the variability
Pooling servers increases the average inventory in a similar
fashion as increasing the variability
Pooling servers reduces the average inventory in a similar
fashion as reducing the variability
Pooling servers reduces the average inventory in a similar
fashion as reducing the variability
Let's say that we are in a system with 10 un-pooled servers and a
variability factor of 1 and we currently have an average
inventory in the queue of 4 since we have a utilization of 80%. If
we want to cut the average inventory in the queue in half, then
what should we do?
Create 2 sets of 5 pooled servers
Pool all servers
,Create five sets of 2 pooled servers
Cut the variability by a factor of 10
Create five sets of 2 pooled servers
Grocery stores have been moving from cashiers to self checkout.
In The Netherlands, one supermarket is taking this to extremes -
watch the video and answer the question.
While the shoppers' opinions vary on self checkout, self
checkout does mitigate the curse of variability to some extent -
which is it?
Pooling multiple queues into one
Lower variability in processing times
Lower average processing times
Less customer cursing
Pooling multiple queues into one
Let's say that you are currently operating close to the inventory
corner on the OM Triangle and you want to get away from there.
What could you do?
Invest in more Capacity
Increase the Utilization
Increase the variability in the service times
Stop collecting Information as this increases the utilization
Invest in more Capacity
So we know where a Fire Station should locate itself on the OM
Triangle, but how about eBay?
,The OM Triangle doesn't apply to eBay since they don't make
anything
Close to the Information corner
Close to the Inventory corner
Close to the Capacity corner
Close to the Information corner
Let's say that your process is currently positioned somewhere on
the triangle (doesn't matter exactly where), and you have just
purchased a wonderful IT system with lots of data that gives you
far more insights into when demand arrives and how long it
takes you to satisfy this demand. If you were to re-position your
process on the triangle accordingly, then in which direction
would you move?
Could be in any direction, it depends on where you were to
begin with
Down
Left
Up
Down
Let's say that your process is currently positioned somewhere on
the triangle (doesn't matter exactly where), and you have just
received a great deal on new machines which are much cheaper
than the ones you are currently using (and are in need of
replacement). If you were to re-position your process on the
triangle accordingly, then in which direction would you move?
, Down (and perhaps to the right as well)
Could be in any direction, it depends on where you were to
begin with
Left (and perhaps up a bit as well)
Left (and perhaps down a bit as well)
Left (and perhaps down a bit as well)
Little's Law Firm has just one lawyer. Customers arrive
randomly at an average rate of 6 per 8 hour workday. Service
times have a mean of 50 minutes and a standard deviation of 20
minutes. How long does a customer spend at Little's Law Firm
on average?
Approximately 48 minutes
Approximately 98 minutes
Approximately one hour
Approximately 75%
Approximately 98 minutes
A local bank branch employs three tellers who can each help a
customer on average in 6 minutes, with a standard deviation of 3
minutes. On average, 24 customers arrive at this bank per hour
(in a random fashion). How long would customers have to wait
if we do NOT pool the employees? (By "not pooling," we mean
we have 3 separate lines forming; one in front of each of the 3
tellers. Assume that a person randomly enters one of the lines -
each of the 3 lines takes one-third of the arrivals - and a person
does not switch lines after entering a line.)
Complete Solutions
The two pictures below show us what happens when we pool
servers & when we decrease the variability.
From these pictures we can clearly see that:
Pooling servers increases the average inventory in a similar
fashion as decreasing the variability
Pooling servers reduces the average inventory in a similar
fashion as increasing the variability
Pooling servers increases the average inventory in a similar
fashion as increasing the variability
Pooling servers reduces the average inventory in a similar
fashion as reducing the variability
Pooling servers reduces the average inventory in a similar
fashion as reducing the variability
Let's say that we are in a system with 10 un-pooled servers and a
variability factor of 1 and we currently have an average
inventory in the queue of 4 since we have a utilization of 80%. If
we want to cut the average inventory in the queue in half, then
what should we do?
Create 2 sets of 5 pooled servers
Pool all servers
,Create five sets of 2 pooled servers
Cut the variability by a factor of 10
Create five sets of 2 pooled servers
Grocery stores have been moving from cashiers to self checkout.
In The Netherlands, one supermarket is taking this to extremes -
watch the video and answer the question.
While the shoppers' opinions vary on self checkout, self
checkout does mitigate the curse of variability to some extent -
which is it?
Pooling multiple queues into one
Lower variability in processing times
Lower average processing times
Less customer cursing
Pooling multiple queues into one
Let's say that you are currently operating close to the inventory
corner on the OM Triangle and you want to get away from there.
What could you do?
Invest in more Capacity
Increase the Utilization
Increase the variability in the service times
Stop collecting Information as this increases the utilization
Invest in more Capacity
So we know where a Fire Station should locate itself on the OM
Triangle, but how about eBay?
,The OM Triangle doesn't apply to eBay since they don't make
anything
Close to the Information corner
Close to the Inventory corner
Close to the Capacity corner
Close to the Information corner
Let's say that your process is currently positioned somewhere on
the triangle (doesn't matter exactly where), and you have just
purchased a wonderful IT system with lots of data that gives you
far more insights into when demand arrives and how long it
takes you to satisfy this demand. If you were to re-position your
process on the triangle accordingly, then in which direction
would you move?
Could be in any direction, it depends on where you were to
begin with
Down
Left
Up
Down
Let's say that your process is currently positioned somewhere on
the triangle (doesn't matter exactly where), and you have just
received a great deal on new machines which are much cheaper
than the ones you are currently using (and are in need of
replacement). If you were to re-position your process on the
triangle accordingly, then in which direction would you move?
, Down (and perhaps to the right as well)
Could be in any direction, it depends on where you were to
begin with
Left (and perhaps up a bit as well)
Left (and perhaps down a bit as well)
Left (and perhaps down a bit as well)
Little's Law Firm has just one lawyer. Customers arrive
randomly at an average rate of 6 per 8 hour workday. Service
times have a mean of 50 minutes and a standard deviation of 20
minutes. How long does a customer spend at Little's Law Firm
on average?
Approximately 48 minutes
Approximately 98 minutes
Approximately one hour
Approximately 75%
Approximately 98 minutes
A local bank branch employs three tellers who can each help a
customer on average in 6 minutes, with a standard deviation of 3
minutes. On average, 24 customers arrive at this bank per hour
(in a random fashion). How long would customers have to wait
if we do NOT pool the employees? (By "not pooling," we mean
we have 3 separate lines forming; one in front of each of the 3
tellers. Assume that a person randomly enters one of the lines -
each of the 3 lines takes one-third of the arrivals - and a person
does not switch lines after entering a line.)
