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
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