Four Variables: Cost, Time, Quality, Scope
Source: https://jchyip.medium.com/four-variables-cost-time-quality-scope-f29b4de8bfdf ↗
Yip's short Medium post revisits the classic project management triangle — cost, time, quality, scope — and argues for being explicit about which of the four is fixed and which is variable in any given project.
The piece is two pages, which is its value: most teams hold the variables informally in their heads, and making the tradeoffs explicit changes the conversation.
For product direction it is a useful reference when a project is going sideways and nobody has admitted which variable is actually fixed.
Yip writes consistently clear pieces on agile and organisational design — his Medium and Substack are worth following. Short, portable, useful.
Central argument
Yip argues that every project is governed by four variables — cost, time, quality, and scope — and that the central mistake teams make is leaving implicit which of these is actually fixed and which can move. His thesis is not that you must sacrifice one variable for another (the usual triangle framing), but that you must name, upfront and explicitly, which variable is the constraint and which are levers. Making that designation visible changes how teams negotiate and absorb pressure when projects encounter trouble.
Critique
The framework assumes that stakeholders who currently keep variables implicit do so out of oversight rather than strategic ambiguity — but in many organisations, leaving the variables unspoken is itself a political choice that protects people from accountability. Yip's prescription (make it explicit) is correct in principle but sidesteps the organisational dynamics that make explicitness threatening in the first place, which limits the piece's practical purchase in contexts where the dysfunction is social rather than cognitive.
Why it matters for product
For a CPO, the framework is most useful not in stable planning cycles but in the specific moment when a delivery is slipping and each function — engineering, design, commercial — is privately assuming a different variable is fixed while negotiating in bad faith. Making scope, not quality, the variable is a product direction decision with downstream consequences for roadmap credibility and team morale; without naming it explicitly, that decision gets made by default at the delivery layer rather than at the leadership level where it belongs.