L11_Variability - Lecture 11 Variability and Waiting Time...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Slide 1 Lecture 11 Variability and Waiting Time
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Slide 2 Le a rning  O b je c tive s Understand different types of waiting time Understand four sources of variability in a queuing system Analyze stationary arrival processes
Background image of page 2
Slide 3 Waiting Times
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Slide 4 Where Are the Queues?
Background image of page 4
Slide 5 Input : Passengers in an airport Customers at a bank Patients at a hospital Callers at a call center Arrival rate = Average demand rate (# flow units/time) Resources : Check-in clerks at an airport Tellers at a bank Nurses at a hospital Customer service representatives  (CRS) at a call center Capacity (# flow units/time) Buffer Processing Queues We are interested in the waiting times  in the queue  and the queue length (inventory) . Flow time = Waiting time (in queue) + Activity Time Queue  Is Made of A Server and A Queue in Front
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Slide 6 The Reality Hello!!!…… ARE YOU THERE ? Thank you for  holding. ... “Soooooome”  time later… Physical queues but also on the phone
Background image of page 6
Slide 7 Blocked calls (busy signal) Abandoned calls (tired of waiting) Calls on Hold Reps processing  calls Answered Calls Incoming  calls Call center Financial consequences Lost throughput Holding cost Lost goodwill Lost throughput (abandoned) $$$ Revenue $$$ Cost of capacity Cost per customer At peak, 80% of calls  dialed received a busy  signal. Customers getting  through  had to wait on  average 10 minutes  Extra phone line expense  per day for waiting was  $25,000. A Simple Queuing System: Call Center Buffer
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Slide 8 7:00 7:10 7:20 7:30 7:40 7:50 8:00 Caller Arrival Time Service Time 1 2 3 4 5 6 7 8 9 10 11 12 0 5 10 15 20 25 30 35 40 45 50 55 4 4 4 4 4 4 4 4 4 4 4 4 Requested Cycle Time = Constant  Interarrival Time = 5 min/call Designed Cycle time = Constant  Service Time  =4 min/call A Somewhat Unrealistic Service Process Flow rate = Utilization =   Demand rate = Arrival rate =  Capacity         = Service rate =
Background image of page 8
Slide 9 Caller Arrival Time Service Time 1 2 3 4 5 6 7 8 9 10 11 12 0 7 9 12 18 22 25 30 36 45 51 55 5 6 7 6 5 2 4 3 4 2 2 3 Time 7:10 7:20 7:30 7:40 7:50 8:00 7:00 Caller 1 Caller 3 Caller 5 Caller 7 Caller 9 Caller 11 Caller 2 Caller 4 Caller 6 Caller 8 Caller 10 Caller 12 0 1 2 3 2 min. 3 min. 4 min. 5 min. 6 min. 7 min. Service times
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/16/2011 for the course OM 335 taught by Professor Jonnalagedda during the Fall '08 term at University of Texas at Austin.

Page1 / 24

L11_Variability - Lecture 11 Variability and Waiting Time...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online