Process Analysis Flashcards
What is a process?
A process transforms inputs into outputs using resources
What is the Process Analysis Methodology?
Process Flow Diagram –> Demand & Capacity Analysis –> Congestion Analysis –> Financial/Decision Analysis
What is an activity?
Activities are actions to complete tasks in a process
What are resources?
These include workforce, tools and equipment
What is the relationship between activities and resources?
Activities are carried out by resources
What is the definition of flow time?
Flow time is the minimum time for a unit to go through the process
What is the definition of resource capacity?
The maximum number of units that a resource can output per unit time
What is the definition of process capacity?
-The maximum flow rate that can be achieved in the process
-This is the minimum of all resource capacities
-Therefore, the process capacity is the same as the bottleneck capacity
What is the equation for utilisation?
-Utilisation= Flow Rate/ Capacity
-Utilisation measures how much a resource actually produces relative to how much it could produce
How do you reduce flow time?
-Decrease work content
-Make some activities parallel
-Reduce waiting time
How do you increase process capacity?
-Decrease the unit load of bottleneck resources
-Move work content from bottlenecks to non-bottlenecks
-Increase net availability
-Never have unnecessarily idle bottlenecks
What is the equation for throughput (flow rate)
Min (demand/input rate, process capacity)
What is the equation for build up rate?
Demand/input rate- process capacity
What is the equation for capacity utilisation?
Input Rate/ Process Capacity
When are the use of build up diagrams appropriate?
When there is predictable variability in demand
When is the use of queuing theory appropriate?
When there is unpredictable variability and arrivals are stochastic
What is the relationship between waiting time (t) and utilisation (u)?
dt/du>0 and d^2t/du^2>0
How can you reduce queues?
-Increase the service capacity
-Reduce seasonality and variation in arrivals
-Reduce the variation in service
How can you increase the service capacity?
-Reduce the length of service time
-Increase staffing or service stations
How can you reduce seasonality and variation in arrivals?
-Price discounts for off-peak hour service
-Appointment systems
How can you reduce the variation in service?
-Standardise the service process
-Reduce the involvement of the customer at the scarce resource
What is Little’s Law?
Inventory= Throughput * Flow Time
When does Little’s Law apply?
Little’s Law applies to any stationary process
What are the sources of variability?
-Inflow of flow units
-Processing times
-Random availability of resources
-Random routing in case of multiple flow units in the process
What is a stationary arrival process?
This is when the inter-arrival time of flow units is constant
What is the flow time for a process that has a queuing system?
Flow time= Time in queue + Processing Time
What are the three factors that affect waiting time?
-Processing time
-Utilisation
-Variability of arrival and process times
What is the capacity when there are multiple servers?
Number of servers/ Processing time
How do you calculate the inventory in a queue?
Queuing time/ Inter-arrival time
What are two cost factors that need to be considered when creating a staffing plan?
-Cost of waiting
-Cost of staffing
What is resource pooling?
This is when two separate systems are combined into a single system
What are the effects of pooling?
-Capacity doubles
-Demand Doubles
-Utilisation stays the same
What are the drawbacks of pooling?
-Workforce must have a broader range of skills which may mean higher wages
-Customers value being treated by the same person
-Pooling can introduce additional setup costs
-Pooling can backfire if it combines different customer classes
