Q1:    The Principle of Invisible Inventory
  • Product development inventory is physically and financially invisible

Q2:    The Principle of Queueing Waste
  • Queues are the root cause of the majority of economic waste in product development

Q3:    The Principle of Queueing Capacity Utilization
  • Capacity utilization increases queues exponentially

Q4:    The Principle of High-Queue States
  • Most of the damage done by a queue is caused by high-queue states

Q5:    The Principle of Queueing Variability
  • Variability increases queues linearly

Q6:    The Principle of Variability Amplification
  • Operating at high levels of capacity utilization increases variability

Q7:    The Principle of Queueing Structure
  • Serve pooled demand with reliable high-capacity servers

Q8:    The Principle of Linked Queues
  • Adjacent queues see arrival or service variability depending on loading

Q9:    The Principle of Queue Size Optimization
  • Optimum queue size is an economic trade-off

Q10:    The Principle of Queueing Discipline
  • Queue cost is affected by the sequence in which we handle the jobs in the queue

Q11:    The Cumulative Flow Principle
  • Use CFDs to monitor queues

Q12:    Little’s Formula
  • Wait Time = Queue Size / Processing Rate

Q13:    The First Queue Size Control Principle
  • Don't control capacity utilization, control queue size

Q14:    The Second Queue Size Control Principle
  • Don't control cycle time, control queue size

Q15:    The Diffusion Principle
  • Over time, queues will randomly spin seriously out of control and will remain in the state for long periods

Q16:    The Intervention Principle
  • We cannot rely on randomness to correct a random queue