Four Variables: Cost, Time, Quality, Scope

4 variables: Cost, Time, Quality, Scope. Cost has diminishing returns. Delaying Time causes coordination problems. Reducing Quality backfires quickly. Controlling Scope is your best option.

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There is a concept in project management called the “iron triangle”.

The Iron Triangle describes the need to trade-off against 3 constraints: Cost, Time, Scope. You can only control 2 out of 3.

However, you may notice that project managers / customers / clients will still try to control all 3 constraints by sacrificing an implicit 4th constraint: Quality.

So instead, there is a model from Extreme Programming called the Four Variables: Cost, Time, Quality, Scope.

Cost. Manipulating cost to accelerate delivery has diminishing returns. There are some quick wins here with faster machines and better equipment. After that, cost ends up being about adding people which generally does not help in the short term (see Mythical Man Month). There are some tactics, like pairing and mobbing, that help with absorbing people more effectively, but even they are not perfect.

Time. Delaying schedule to accommodate scope generally causes broader coordination problems. If there are any dependencies on a delivery, delays tend to cascade throughout a…