There is a lot of material available on agile estimation; some of it indicating that, traditional parametric models of estimation are not so effective. I’m not an outright hater of “parametric models” and am of an opinion that, they are very useful in certain scenarios. However, at other times; lean estimation processes and models which give higher importance to the experience of the team members involved are what I personally prefer.
To efficiently utilize the past experience, the tasks need to be broken down to a level where human mind can map it easily to something done in the past. Various agile experts say tasks of upto 8 hours duration would be most effective. Discrepancies start flowing in for anything more than that.
As various agile methodologies suggest, estimation is a team effort. This means, use of efficient tools to quickly come to a rough estimate is very important so as to save the crucial “person-hours”.
Fishbone diagrams(also known as cause-effect, Ishikawa, herringbone diagrams) have traditionally been used mainly for doing root-cause analysis; as far as the software world is concerned. However,I’ve also found it to be equally effective in granulation of the features of a project to comfortable levels as mentioned above. Thinking differently, a successful project is an effect of all the modules (causes) being successful.
Let’s explore the concept with a fishbone diagram for a Human Resources(HR) management System.
For the sake of simplicity, project, product and system indicate the main task at hand. It could be the deliverable for a particular iteration as well. Moreover, only one of the modules have been broken down.
Step1: Put the project name on the backbone in place of “root” or “effect”.
Step2: Break the project into a maximum of 6 logical parts. Let’s call them modules.
Step3 : Check if each of the modules can be completed within 8 hours. If not, break each of the “bigger” modules into 6 parts. Continue the process till you get all the “branches” with estimates less than or equal to 8 hours. The moment you get a branch which would take less than or equal to 8 hours, mention the estimates on the branch.
Step4: Stick the fish-bone diagram in a place where everyone in the team can see it.
2-3 levels of drilling down should be more than enough for many of the systems.