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In John Stenbeck’s book “PMI-ACP and Certified Scrum Professional Exam Prep and Desk Reference”, he creates an “agile project management process grid” which describes 87 processes used in agile project management.   These processes are divided into five process groups (Initiate, Plan, Iterate, Control, and Close), which are analogous to the five process groups in traditional project management, and seven knowledge areas which can be mapped, more or less, onto the ten knowledge areas in traditional project management.

Today’s post is about an estimating technique called ideal days or sometimes referred to as ideal time.   Actually it’s the start of an estimating technique, which is refined in using actual days or actual time.

What are ideal days?   They are the unit of measure expressing the work time required to complete an activity assuming that there are no interruptions so that work can be completed with 100% efficiency.    Now how realistic is a work day that assumes no interruptions?   Not very.

That’s why the next step in estimating the work time required to complete an activity is actual days.    This is a refinement of the ideal days estimate, but this time with the assumption that typical interruptions will occur and reduce the 100% efficiency rate to a lower rate.

However, as John Stenbeck points out in his book is that even this correction is difficult to estimate.    How does one estimate a “typical interruption”?    How does that typical interruption actually reduce the efficiency?   It’s a greater idea for estimation, but harder to implement than it looks.

This is why the preferred method is to use story points, process 3.12.  Although this seems to be less precise because it is a relative, rather than an absolute, estimating method, it ends up using the collective brainpower of the group to come up with the size of user stories relative to each other, from which a total estimate can be made using the next process, 3.14 Affinity Estimating, which is the subject of the next post.

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