Estimating Project Duration

13 July

Projects are risk magnets. Why is that? It’s because projects undertaken by organizations typically have not been done by that organization and the stakeholders involved do not know the right questions to ask to avoid the risks especially when it comes to estimating project duration.

When my clients or colleagues invariably ask, “How long do you think this effort might take?” I tell them I don’t know how long it will take then I ask a host of questions:

What is it you want to accomplish and how soon do you want to get there?

What is the priority of this project relative to other organizational initiatives?

What resources will be assigned to the project?

How many days a week will they be assigned to the project?

What’s your tolerance for task slippage?

Will change requests be evaluated to increase scope or will all change requests go to the parking lot?

What are the business requirements and scope of the initiative?

Essentially do you want a house with 2 bedrooms and 2 baths or are you looking for a 4 bedroom, 3 bath house with a finished basement and a sunroom that you would like to move into in 4 months?

Oh yeah one of the questions I usually ask is; what estimating and planning processes have you used on other initiatives? We all know the answers to that don’t we?

Unless that project is something I’ve performed many times before – under very similar conditions each time, providing an accurate estimate can be quite elusive. As I strive to imagine all of the stages and steps of a project, as well as fathom the unknown variables or things that could go awry, it’s no wonder that I hardly ever guess 100% correctly, particularly for new endeavors. I mean who excels at predicting the time, funding, and resources your projects will require? And we all know once a date is stated it becomes cemented in top management’s head as an expectation and not an estimate.

Whether your company aims to develop a new product or service, update an existing system, or launch a new Web site, these undertakings will require people, schedules, funding, resources, requirements, testing, revising, implementation, evaluation, and many other elements.

One of the most critical mistakes a project manager can make is to provide any estimate without consulting with the team who will be doing the work. With all of the emphasis we place on creating accurate estimates we still seem to have difficulty developing realistic predictions of our time and effort and the ones that can do that best are the ones assigned to do the work.

To improve the accuracy of your estimates consider the following:

Create and use planning documents, such as a business requirements document and project plans that outline the major activities required to satisfy the requirements.

Ask team members to use more than one method to arrive at an estimate, such as optimistic, “expected”, and pessimistic and look for a midpoint among all of them.

Document all assumptions. You will never know all the details of a project, so it’s important to identify a set of assumptions to accompany your estimate calculations. For example a common assumption I use on most projects is: Planning and estimating of timelines are based on the assumption that J. Smith and M. Jones will be allocated to the project 3 days a week.

Build in a buffer. Communicate upfront to all stakeholders that you are building in a buffer of 15-20% of the total calendar days of the project to account for the unexpected and Murphy’s Law.

Document requirements. Always incorporate the time required to elicit and define business requirements as a separate phase of the project. Trying to estimate the duration of the project without knowing the requirements is a planned death march.

Other things to consider when estimating project duration are:

Factor in available workdays. Take into account holidays, vacations and training.

Determine how many resources will be applied to each activity. In general, the more resources you can apply to activities, the quicker they can be completed. Obviously two resources may be able to complete an activity faster than one person (but it may not be twice as fast).

Identify resource constraints. When you build your initial work plan, identify the activities that can be done sequentially and those that can be done in parallel. If you have enough resources, all of the parallel activities can, in fact, be done in parallel. However, if you don’t have enough resources (you rarely do), you’ll find that some of the parallel activities need to be done sequentially, since the same resource needs to be assigned. Meet with key stakeholders and explain the resource constraint issue and obtain additional resources or approval that result in extending the duration further than what they might initially expect.

Estimating is not to be taken lightly, but we must always remember that estimates will be wrong and it is how we re-adjust the plan and use what we learned that will improve estimating in the future.


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