core Estimated learning time: 10 h

EC-14.3 Trade-offs, Decided on Purpose

You can name the axes a design is trading between, compare options against weighted criteria without pretending the result is objective, estimate before measuring, and record a decision so that it can be revisited rather than re-argued.

Before:EC-13. Laboratory Practice, in SequenceUnlocks:EC-15. Capstone, in Two StagesEC-17. Industry and Research Experience

Every interesting engineering decision is a trade, and most are made implicitly by whoever happened to write the first version. This topic makes them explicit. The recorded decision in particular is worth more than it looks: a project that can say why it chose something can change its mind cheaply, and one that cannot is stuck with an accident.

Work through these

  • Naming the axes before comparing anything

    Cost against performance, power against speed, size against serviceability, time against risk. Writing the axes down first is what stops a comparison from being decided by whichever option was described more enthusiastically.

    NPTEL: Product Design and Innovation (IIT Guwahati) · Course
  • A weighted comparison, and its honest limits

    Scoring options against weighted criteria organises a discussion and does not settle it. The weights are judgements, so the table's value is in making those judgements visible rather than in its total.

    NPTEL: Project Management (IIT Kanpur) · Course
  • Estimating before measuring, and being wrong usefully

    An order-of-magnitude estimate of power, cost or time takes minutes and tells you which options are not worth investigating. Being wrong by a factor of two is fine; being wrong by a factor of a hundred is the point.

    NPTEL: Product Design and Innovation (IIT Guwahati) · Course
  • Reversible and irreversible decisions

    Some choices can be changed next week and some are fixed once a board is manufactured. Spending analysis in proportion to how hard a decision is to undo is the most useful rule in this topic.

    NPTEL: Project Management (IIT Kanpur) · Course
  • Risk, and doing the frightening part first

    The part you are least sure about should be prototyped earliest, not last. Projects fail late because the risky element was deferred until there was no time to respond to what it revealed.

    NPTEL: Project Management (IIT Kanpur) · Course
  • Recording a decision so it can be revisited

    What was decided, what the alternatives were, and why. A page per significant decision means a later question is answered by reading rather than by re-arguing it from memory.

    NPTEL: Technical Communication for Engineers (IIT Roorkee) · Course

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