Getting ready

Before starting, it is important to have an understanding of how long standard tasks take within your organization and which algorithms are used for estimation.

How to do it...

Once you have created the work breakdown structure, reopen this spreadsheet:

How it works...

Identifying the task drivers, base hours, and a standard estimating tool makes it easier to get a realistic effort for your project. This is, however, only an effort for one resource, and not duration. For an extra step, you will need to add dependencies and resources to a calendar of working days and additional project management time.

There's more...

Many project estimation algorithms are used. The sample spreadsheet uses the following:

Weighted Average with Estimate (E) takes into account the optimistic, pessimistic, and most likely estimates for each task.

Standard Deviation determines variation from the average. The Confidence levels shown in the preceding bullet list indicate how likely you are to achieve your goals within your estimate, if you combine the different values.

Therefore, if you need an estimate with about 50% probability achievability to actual, then using the Weighted Average (E) value would suffice. If you required an 85% probability of being able to deliver within your estimate, then Weighted Average+Standard Deviation should be used. For information systems, normally 95% is the standard to utilize.

Over a period of time, you can refine these calculations to reflect your environment more accurately once you have the actual values, which can replace the effort drivers and quantity.

Additional information for this topic can be found at:

http://en.wikipedia.org/wiki/Three-point_estimation.