Glossary Decisions & governance
What is a trade study?
A trade study compares design alternatives against weighted criteria to choose one, and records why the others were set aside.
Also called trade-off study, trade-off analysis.
Trade study
A trade study is a structured comparison of design alternatives against the criteria a design must balance, such as mass, cost, risk, performance and schedule. The criteria are often weighted, each alternative is scored against them, and the result is checked for how sensitive it is to the weights and assumptions. The output is a choice and the rationale behind it.
Why it matters
Most design choices trade one property against another. A trade study makes the criteria explicit before the answer is known, and its record explains later why an option lost, which matters when a requirement or an assumption changes.
How it goes wrong
- Choosing an option and keeping no record of why
- Adjusting criteria or weights after seeing which option wins
- Keeping the study in a file that is not connected to the design it decided
In Cairn
Cairn has no trade-study tool: no criteria, weights or scores. It keeps the outcome next to the design. In the Dendritic lens, a node's parts are what was chosen, and beside them sit the alternatives set aside, each with what it was weighed against, why it lost, the first principle that decided it, the kind of decision and its phase, along with the options still open. You record these in the inspector, or ask AI to suggest alternatives through Change Review.
Questions
- Is a trade study the same as a Pugh matrix?
- No. A Pugh matrix is one way of comparing alternatives. A trade study is the wider activity, and may use a Pugh matrix, weighted scoring or detailed analysis.
- Why keep the alternatives that lost?
- Because the reasons outlive the decision. When a requirement changes, the reason an option lost may no longer hold, and the record shows which decisions to revisit.
See it on your own system.
Describe what you are building and Cairn interviews you, then builds the first model with you.