Module 4: Responsiveness

Question 1

Inter-arrival time

Answer 1

Amount of time between subsequent arrivals

Question 2

Waiting time formula (1 server)

Answer 2

Time in queue = Service time factor * Utilization factor * Variability factor T[q] = p * u/(1-u) * (CV[a]^2 + CV[p]^2)/2

Question 3

Waiting time formula (m servers)

Answer 3

Question 4

Utilization formula (m servers)

Answer 4

u = (1/a) / (m * (1/p)) = p / (a*m)

Question 5

Inventory in queue formula

Answer 5

I[q] = (1/a) * T[q] I[p] = u*m I = I[q] + I[p]

Question 6

Limitations of pooling

Answer 6

1) Assumes flexibility 2) Increases complexity of workflow 3) Can increase the variability of service time 4) Interrupts the relationship with the customer

Question 7

Sequencing

Answer 7

Defining priority rules to determine who should be served first

Question 8

Weakness of appointments

Answer 8

Don’t solve supply/demand mismatch problem. Shift inventory from waiting room to home.

Question 9

Flow Time Efficiency

Answer 9

%VAT = Total value add time of a unit / Total time a unit is in the process

Question 10

Process Mapping: How to redesign a service process

Answer 10

1) Move work off the state (eg. online check-in) 2) Reduce customer actions (eg. Dr. office check-in) 3) Eliminate a step (eg. Hertz car pick-up) 4) Avoid fragmentation (eg. Loan processing) 5) Re-sequence activities (eg. Starbucks pay first) 6) Move waiting outside of line (eg. buzzer at restaurant, appointment) 7) Set expectations (eg. Disney)

Question 11

Waiting problems

Answer 11

Utilization has to be less than 100%, variability impacts flow time

Question 12

Loss problems

Answer 12

Demand can be bigger than capacity, variability impacts flow rate

Question 13

Erlang loss formula

Answer 13

Used to estimate potential loss of throughput if the occupancy or utilization of the resource is too high