[nevergetenglish]

To estimate the time required to design your system you need to estimate the variance of the time required. A well known result is that the variance of a sum of independent variables associated to independent problems is the sum of the variances of the subproblems.

What this mean in practice? It means that you should try to decompose your problem in independent and dependent subproblems (perhaps associated to features). Independent subproblems their variance, the formula for dependent problems depends of the correlation between them.

What I am trying to say is that if you know a little math and have an intuitive knowledge of the structure of the problem divided in sub-problems you could make a much better estimate of the variance (and this mean there is much less uncertainty in the delivery time). One could design a program that constructs a graph and a knowledge base of previous programs that you have designed. The graph edges should be weighted in accordance with the correlation factor of dependency of those components.

Now that I am writing this, it seems very likely that someone has implemented such a scheme to estimate time delivery. Perhaps there are start-ups using this system to estimate delivery time, since all this is basic math.

Edited: Mostly grammar.