SCM 300 Chapter 5: Queueing Systems, Retail Layout, and VMI

What two costs does a queue manager balance?

Customer time spent waiting versus employer cost of servers.

What are the three parts of a waiting-line system?

Potential customers, waiting queue, and service facility.

What is an example of a finite input source?

A retailer of jumbo jet aircraft.

What is an example of an infinite input source?

McDonald's; its pool hardly changes when one customer arrives.

What is balking?

Not joining after seeing a line.

What is reneging?

Leaving a queue after joining.

What is jockeying?

Moving between separate queues.

What is the essential format for λ and μ?

Customers or transactions divided by time.

What is the professor's emergency-room queue rule example?

Priority service: emergencies may be served ahead of FCFS order.

If there is 1 arrival every 12 minutes, how many arrivals per hour?

5 arrivals per hour.

If there is 1 transaction each 3 minutes, how many transactions per hour?

20 transactions per hour per server.

What does rho = .68 mean?

A single server is busy 68% of the time.

Why convert hours to minutes in t values?

A time formula using hourly rates produces hours; multiply by 60 for minutes.

Which counts include a customer being helped?

System measures n_s and t_s, not queue-only n_l and t_l.

In a system with four chairs plus one server, what is P?

P6: one served, four seated, at least one standing.

What is the single-server state probability formula?

P(n)=(1−ρ)ρ^n, where n is in the whole system.

Fewer than 2 in system means which states?

P0 + P1.

Will students derive 2/3-server equations?

No; professor provides a scenario chart to interpret.

With three servers, what are the served immediately states?

P0, P1, P2 in the three-server column.

What does the Burger King example test?

P5: 3 being served + 2 waiting.

What should you read first in the example?

Read lambda and mu first, then calculate utilization and queue times.

What is the call-center arrival rate in the problem set?

120 calls per hour.

What is the arrival rate given in the long chart example?

17 customers per hour.

If one worker handles 200 in 8 hours, what is μ?

25 customers per hour.

For λ=17, μ=25, what is ρ?

17/25 = 0.68.

For λ=17, μ=25, what is the average t_s?

1/(25−17) hours = 7.5 minutes.

For λ=17, μ=25, what is the average t_l?

ρ × t_s = .68 × 7.5 = 5.1 minutes.

For λ=17, μ=25, what is the average n_s?

17/(25−17) = 2.125 people.

For λ=17, μ=25, what is the average n_l?

.68 × 2.125 = 1.445 people.

For three servers, what is the immediate service chance?

1 − (P0 + P1 + P2).

What does the professor's chart example show?

P0+P1+P2 = 96.6%.

Why is retail called a manufacturer of experiences?

Store operations, staff, design and logistics create the shopping experience.

What is the purpose of Safeway produce near the entrance?

Fresh visual appeal and a high-profit shopping category.

Why is Safeway meat toward the rear?

High-profit meat area encourages traversal through aisles.

Why is Safeway dairy/bakery far from the entrance?

Frequent necessities lead shoppers past additional merchandise.

How does Target's layout contrast with grocery stores?

Target has central clothing/high-margin; grocery has high-profit departments often perimeter.

What store did the lecturer compare to a maze?

IKEA, where a guided route increases exposure to merchandise.

What is the benefit of vendor-managed inventory (VMI) to the supplier?

Vendor accepts negotiated stock monitoring and replenishment tasks.

What does VMI allow the vendor to see?

Sees actual demand, responds to stock levels, improves planning.

What is a risk of VMI regarding the vendor's image?

Retailer's image; shoppers may assume vendor staff are store staff.

What should a VMI agreement clarify?

Process, schedule, IT, quality, worker behavior and responsibilities.

Why is vendor employee turnover a problem?

Store-specific knowledge and good working relationships may be lost.