Project managers should look at estimation as if it were a triangle. The three points are scope, cost, and time, and if you are tightening the constraints of one, the length of the other two will have to increase. This is what keeps the triangle intact. Anthony A. DeMarco proposes this triangle model while stressing the importance of estimation to the project manager. He also states that projects launched without an initial estimate are five times more likely to fail. Why? Because they aren’t asking themselves these five key questions:
- What is the measure of scope?
- What is the productivity?
- What is the resource availability assumption?
- What are the most significant reality factors making this different than the norm?
- What is the uncertainty of the parameters and the risk in the estimate?
If you’re skipping estimation, it’s time to figure out what it will cost you. Just like decreasing the time frame for the project ups the cost and need for productivity, so does decreasing estimation time increase the chance of mistakes later. DeMarco advises that project manager look at the whole triangle, instead of just one line of it.