7. QUANTITATIVE PROCESS ANALYSIS

Question 1

flow analysis

Answer 1

• average time it takes between the moment the entire process starts and the moment it completes
  -waiting time + processing time
  = Theoretical cycle time (TCT)
  (processing time; average time a case would take it there was no waiting time at all)

-CT efficiency = Ratio of overall processing time, referred to as theoretical cycle time (TCT), relative to the overall CT

Question 2

critical path method

Answer 2

• critical path → sequence of process that determines the theoretical cycle time of the process
  -identifies the critical path based on the notions of:
  ● early start/finish → forward pass
  ● late start/finish → backward pass

Question 3

Little’s law

Answer 3

• total cycle time of a process is related to the arrival rate 𝜆 and the work-in-process WIP

arrival rate= avg nº of new process instances

WIP= avg nº of active process instances

Question 4

characteristics of little’s law

Answer 4

Little’s law holds for any stable process (the amount of work doesn’t grow beyond control)

Question 5

capacity and bottlenecks

Answer 5

Theoretical capacity= max nº of instances that can be completed per time unit by a resource pool (p)

-characteristcs:
● theoretical capacity of a resource pool implies that this pool is working at full capacity
● resource pool with the minimum theoretical capacity is called the bottleneck of a process

Question 6

limitations of flow analysis

Answer 6

• Presented equations for calculating cycle time (CT) work only for block-structured process models

-Need to estimate the average CT of each task in the process model:

2 approaches:
1. to address this obstacle is based on interviews with, and/or observations of, process participants

2. to collect logs from the IT systems used in the process

• Critical assumption that level of resource contention are stable over the long run

Question 7

queueing theory

Answer 7

Collection of mathematical techniques to analyze systems with resource
contention, which inevitably leads to queues

● expected length (Lq)
● expected waiting time (Wq)

Question 8

queuing system

Answer 8

consists of:
● 1 or multiple queues
● service that is provided by one or multiple servers
● elements inside a queue = jobs or customers

Question 9

system types

Answer 9

-Single-line → M/M/1
-Multi-line → M/M/c (c = number of servers)

Question 10

limitations of queuing analysis

Answer 10

• Assumption that inter-arrival times follow a negative exponential distribution
  –> shorter inter-arrival times more likely

-Presented queuing analysis techniques can only deal with one process task at a time
–> queuing network more suitable

Question 11

process simulation

Answer 11

use the process simulator for:
- generating a large number of hypothetical instances of a process
- executing these instances step-by-step
- recording each step in this execution

Question 12

output of a simulator includes

Answer 12

-logs of the simulation
-statistics of cycle tymes, avg times, avg resource utilization

Question 13

input parameters

Answer 13

-processing time of each task
-resource pool responsible for performing a given task
-branching probability for every gateway
-starting date and time of simulation

Question 14

common probability distributions

Answer 14

• fixed values (rare)
• exponential distribution
• normal distribution