You have options for estimation, once you have met the preconditions. If you don't have the feature set in a ranked order, you are in trouble. That's because if you use any lifecycle other than an agile lifecycle, the feature order matters to your estimates, and the team will discuss the feature order in addition to the size of the estimates. That will make your estimation time take longer and your team will not agree. It all starts to get stickier and stickier.
When You Have a Decreed Date
It's fine to live with a decreed date—that means you get to manage the features. Now, you have a choice. You can work in iterations or in flow (kanban). Let's assume you work in iterations for now.
Use Timeboxes, Better Your Estimate as You Proceed
If you have worked on a project like this, with this exact team before, so that you can use this team's velocity, go ahead and use this team's velocity and estimate the entire backlog with the team. I would timebox this effort to no more than 2 hours total. It's not worth spending any more time on it, because your estimate is bound to be wrong. Why? Because this is new work you have not done before.
This estimate is the first date you cannot prove you cannot make. This is your most optimistic estimate. It is not the most likely estimate, nor is it the most pessimistic estimate. Well, unless you are all Eeyore-type people, in which case it might be the most pessimistic. But, I doubt it. I would take that estimate, and say to my manager, “Here is an estimate that I have about 50% confidence in. I will know more at the end of the third iteration.”
The team tracks its velocity for three iterations and re-estimates the entire backlog again, and see what it has for an estimate again, and compares what it now knows with what it knew before. Now, you have something to compare. You now ask the team how much confidence they have in their estimate. Report that to management. Maybe they have 50% confidence, maybe they have less. Maybe they have more. Whatever they have, report that to management.
Repeat estimating the remaining backlog until you get to 90% confidence.
When You Have a Decreed Date and a Decreed Backlog
Some of you are saying, “JR, my manager has also decreed the feature set.” Fine. As long as your manager has decreed the feature set in rank order, you can make this work.
You still need to know in what order your manager wants the features in. Why? Because if you look back at the project pyramid and the preconditions in Part 1, several things can occur:
- Your customers/manager may not want all the features if you demo as you proceed
- Your customers/manager may not want to pay for all of features as you proceed, especially if you provide an estimate and demo
- You are getting dangerously close to having too many fixed constraints on this project, especially if you have a fixed number of people and a fixed working environment. Do you also have a fixed cost? You are in the danger zone! I can guarantee you that something will not be fixed once your management or customers see the number of defects.
Obtain Data First, Then Argue
If the manager has decreed the date and the feature set why are you estimating anything? Get to work! This is when using timeboxes or kanban and determining your true velocity and performing demos is useful to show progress so your management can see what you are doing. They have no idea if their decrees/wishes are reasonable. I don't think there's much point in fighting with them until you've accomplished half of the ranked backlog or worked through half of the schedule. Once you've done half of the backlog or half the schedule, now you have data and can see where you are.
Now you can take your data, and use the previous option and provide estimates for the rest of the backlog with confidence ranges.
When I've been the project manager for imposed dates and imposed backlogs, I've explained to management that we will do our best, but that we will maintain a reasonable pace from the beginning and when we are halfway through the time and the backlog I will report back to management where we are. Did they want to know where we are a quarter of the way instead, where we have more flexibility?
That changes the conversation. Sometimes they do, and sometimes they don't. It depends on how crazed the management is. I also protect the team from multitasking (none allowed). I am the Wall Around the Team, protecting the team from Management Mayhem.