SCM 300 - MODULE 05
Goal of waiting line management
Balance the cost paid by the customers (time) with the cost paid by the company
(money paid to maintain the system).
Parts of a waiting line system
input source, waiting line, service facility
Input Source
this is the population of people that might want service
Waiting Line
The area which customers wait for service
Service Facility
The area in which customers actually receive service
4 Managerial Considerations in Queues
Customers - How many are there? How quickly are they arriving?
The waiting lines - What type of lines? How many lines?
Employees - Who's working in the system? How many? Skill level and speed?
Service facilities - How effective and efficient is the process? Tools?
Basic waiting line terminology
queue: line.
channel: line. refers to the number of lines available at each step.
, phase: a single step in a process.
infinite population of customers: the number of possible customers that may
come into the store is very high (or unlimited.) When a customer enters the
system, the odds of another entering the system are not impacted in any
significant manner.
finite population of customers: The number of customers is limited. Example: If
you have a bus company that has 10 busses, then your company's repair shop
has a finite population of 10 busses. If 1 bus is in the shop only 9 others are left
in the population. The odds of a 2nd bus entering the system decline.
balking: when a potential customer sees the line, but never joins the line because
they think it looks too long and/or too slow
reneging: when a customer joins the line, gets frustrated and leaves the line
Single-server formulas and calculations (in text: a sampling queuing model)
Arrival (Lambda) rates: define and calculate
number of customers arriving / unit of time
Service (Mu) rates): define and calculate
number of customers helped / unit of time
Percentage of Time Worker is Busy
rho = lambda/ mu
average number of customers in the line (nl)
= rho[lambda/(mu-lambda)]
average amount of time a customer waits in the line (tl)
rho[1/(mu-lambda)]
Goal of waiting line management
Balance the cost paid by the customers (time) with the cost paid by the company
(money paid to maintain the system).
Parts of a waiting line system
input source, waiting line, service facility
Input Source
this is the population of people that might want service
Waiting Line
The area which customers wait for service
Service Facility
The area in which customers actually receive service
4 Managerial Considerations in Queues
Customers - How many are there? How quickly are they arriving?
The waiting lines - What type of lines? How many lines?
Employees - Who's working in the system? How many? Skill level and speed?
Service facilities - How effective and efficient is the process? Tools?
Basic waiting line terminology
queue: line.
channel: line. refers to the number of lines available at each step.
, phase: a single step in a process.
infinite population of customers: the number of possible customers that may
come into the store is very high (or unlimited.) When a customer enters the
system, the odds of another entering the system are not impacted in any
significant manner.
finite population of customers: The number of customers is limited. Example: If
you have a bus company that has 10 busses, then your company's repair shop
has a finite population of 10 busses. If 1 bus is in the shop only 9 others are left
in the population. The odds of a 2nd bus entering the system decline.
balking: when a potential customer sees the line, but never joins the line because
they think it looks too long and/or too slow
reneging: when a customer joins the line, gets frustrated and leaves the line
Single-server formulas and calculations (in text: a sampling queuing model)
Arrival (Lambda) rates: define and calculate
number of customers arriving / unit of time
Service (Mu) rates): define and calculate
number of customers helped / unit of time
Percentage of Time Worker is Busy
rho = lambda/ mu
average number of customers in the line (nl)
= rho[lambda/(mu-lambda)]
average amount of time a customer waits in the line (tl)
rho[1/(mu-lambda)]
