I had access to information about historical projects, so I compared the actual amount of time taken to the estimated time at the beginning, for every software project in the history of my organization.
I found that on average, things take twice as long as expected.
So, I was like, now I know how to estimate any project. I figure out what seems reasonable based on known factors...and double it.
A way to look at this is the "unknown unknowns" of anything empirically average to a 100% overshoot.
But this doesn't fly with the project managers I work with, because they can only see that as illegitimately padding an estimate.
I found that on average, things take twice as long as expected.
So, I was like, now I know how to estimate any project. I figure out what seems reasonable based on known factors...and double it.
A way to look at this is the "unknown unknowns" of anything empirically average to a 100% overshoot.
But this doesn't fly with the project managers I work with, because they can only see that as illegitimately padding an estimate.