Garbage In, Garbage Out
quote
In other words, cost-benefit analysis is only as good as the numbers you put into it. In computer science, there is a model describing this phenomenon: garbage in, garbage out. If your estimates of costs and benefits are highly inaccurate, your timelines don't line up, or your discount rate is poorly reasoned (garbage in), then your net result will be similarly flawed (garbage out).
From
Chapter:
Decisions, Decisions
Section:
Weighing The Costs And Benefits