About
Given the individual tasks' estimations (in hours), calculates the total estimation for the whole
project. It attempts to do the right thing, when summing up estimations, treating each individual
estimate as a continuous random variable (see Math), and applying a formula from Steve McConnel's
book "Software Estimation: Demystifying the Black Art".
Doing the math right though requires providing a range for an individual estimate instead of a
single number: you'll be asked for the best case, the most likely case, and the worst case hours.
By the way, the probability of a task taking exactly X hours to finish is exactly zero (see Math
again ;).
Also, a subjective confidence factor is provided for each task's estimation, in percent, within
the range (0, 100) -- excluding 0 and 100. Normally, you should be pretty confident in the most of
your tasks' estimations, specifying confidence factors above 90% for them. Only a smaller part of
tasks should have 90% and below. Anyway, that's a just fine tuning mechanism; you may well ignore
it, and simply assign, say, 95% confidence to all the tasks.
The number E you get from total75PercentLikelyHours()
means that there's a 75% probability that
your project will take not more than E hours.
Installation
Node.js:
$ npm install estimate-tasks
Web browser:
$ bower install estimate-tasks
API
Node version:
var et = require("estimate-tasks"),
total = et.total75PercentLikelyHours([{
bestCaseHours: 1,
mostLikelyCaseHours: 1.5,
worstCaseHours: 4,
confidencePercent: 99.9
}, {
bestCaseHours: 8,
mostLikelyCaseHours: 10,
worstCaseHours: 12,
confidencePercent: 66
}, {
bestCaseHours: 2,
mostLikelyCaseHours: 3,
worstCaseHours: 4,
confidencePercent: 95
}]);
In the browser you have to include the
lib/calc.js script. Then:
var et = window["estimate-tasks"];
Testing
Test-driven with Mocha. Under Node, say:
~/estimate-tasks(master)$ npm test