Scrum & Waterfall: An At-a-Glance Comparison of Their Underlying Principles

Chapter three (Agile Principles) in my Essential Scrum book describes the agile principles that underlie Scrum and compares them with those of traditional, plan-driven, sequential product development. Many people have asked me to share the summary comparison table at the end of that Chapter. It is reproduced below.  Free to comment on it!

Topics Plan-Driven Principles Agile Principles
Similarity between development and manufacturing Both follow a defined process. Development isn’t manufacturing; development creates the recipe for the product.
Process structure Development is phase-based and sequential. Development should be iterative and incremental.
Degree of process and product variability Try to eliminate process and product variability. Leverage variability through inspection, adaptation, and transparency.
Uncertainty management Eliminate end uncertainty first, and then means uncertainty. Reduce uncertainties simultaneously.
Decision making Make each decision in its proper phase. Keep options open.
Getting it right the first time Assumes we have all of the correct information up front to create the requirements and plans. We can’t get it right up front.
Exploration versus exploitation Exploit what is currently known and predict what isn’t known. Favor an adaptive, exploratory approach.
Change/emergence Change is disruptive to plans and expensive, so it should be avoided. Embrace change in an economically sensible way.
Predictive versus adaptive The process is highly predictive. Balance predictive up-front work with adaptive just-in-time work.
Assumptions (unvalidated knowledge) The process is tolerant of long-lived assumptions. Validate important assumptions fast.
Feedback Critical learning occurs on one major analyze-design-code-test loop. Leverage multiple concurrent learning loops.
Fast feedback The process is tolerant of late learning. Organize workflow for fast feedback.
Batch size (how much work is completed before the next activity can start) Batches are large, frequently 100%—all before any. Economies of scale should apply. Use smaller, economically sensible batch sizes.
Inventory/work in process (WIP) Inventory isn’t part of the belief system so is not a focus. Recognize inventory and manage it to achieve good flow.
People versus work waste Allocate people to achieve high levels of utilization. Focus on idle work, not idle workers.
Cost of delay Cost of delay is rarely considered. Always consider cost of delay.
Conformance to plan Conformance is considered a primary means of achieving a good result. Adapt and replan rather than conform to a plan.
Progress Demonstrate progress by progressing through stages or phases. Measure progress by validating working assets.
Centricity Process-centric—follow the process. Value-centric—deliver the value.
Speed Follow the process; do things right the first time and go fast. Go fast but never hurry.
When we get high quality Quality comes at the end, after an extensive test-and-fix phase. Build quality in from the beginning.
Formality (ceremony) Formality (well-defined procedures and checkpoints) is important to effective execution. Employ minimally sufficient ceremony.