This week the tweets looked at at project estimation using the estimating by analogy method.

Estimating by analogy is done by comparing the effort for tasks / deliverables of the current project to past projects with similar traits.

So the first thing you need for estimating by analogy is data from past projects. Actual data is the best if you or others has tracked it. If you don't have a lot of past data you can still do the analogy method by using data from industry sources. Another way to get data for the is to estimate standard elements of the project such as web pages, interfaces etc. to develop base numbers

Once you have your baseline numbers you can now build the first draft estimate. Start by identifying elements to be built for the project. Then for each element identified categorize the complexity as high, the same, or low compared to the base element. Now you need to determine the time or effort change based on the complexity. E.G.the baseline web page takes 16 hrs to develop and unit test.

You can the say that a low complexity web page will take 12 hours and a high complexity will take 24 hours.

Do this for all the elements and then add up the numbers. Add in test, rework, and deployment time. This will give you your first draft estimate. It is best if the team helps with the estimates as the more expertise used the more accurate and complete the estimate will be. If you have multiple people estimating a particular element make sure to use the average numbers and not the best case or smallest. You want the estimates to be reasonable and doable.