from: The Economist
A Project Duration Formula
Combine the awareness of obstacles and their need to have buffer time built into the project time line with a good project duration estimation formula and you'll begin to be more accurate in your ability to meet those project deadlines. Snead and Wycoff provide a simple way to calculate a realistic duration for the project or for the individual next actions within it:
• Te = Realistic time estimate
• To = Most optimistic time estimate (the Sunny Side estimate with no setbacks)
• Tp = Most pessimistic time estimate (with every obstacle happening)
• Tm = Most probable time estimate (this makes you think realistically; some setbacks happen, others don't)
Let's say we have a project of developing a departmental newsletter. The variables break down as follows:
• Tm = 14 days
• To = 10 days
• Tp = 30 days
The calculation would be:
Te = (10+(4X14)+30)/6
The best estimated duration for the project would be 16 days.
By applying both strategies of building in buffer time for obstacles and using a good project duration formula, consistency in estimating deadlines will develop. Being known as someone whose projects come in on time and under budget is always a career helper and improves one's perceived competence. Besides, it also makes us more confident in our abilities and that confidence helps to improve our performance, which boosts our confidence, which, again, elevates our performance. As one can see, there is such a thing as an upward spiral.