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Each month, Tom Mochal, President of TenStep, Inc. presents project management tips and techniques for planning and managing a project. TenStep, Inc. has a comprehensive, scalable project management process called TenStep (www.TenStep.com), as well as a project lifecycle process called LifecycleStep (www.LifecycleStep.com). Tom has also published a popular book called Lessons in Project Management that can be purchased at www.TenStep.com. Pipeline readers receive 20% off any TenStep or LifecycleStep purchase by entering the coupon code of "Pipeline" in their purchase.
The estimation process is an art and a science. However, once you learn good estimating processes and techniques, you will hopefully be able to move more toward the “science” side of estimating and rely less on the “art” side. You can get better and better at estimating, but by nature you can never be perfect. Here is a list of common estimating problems that should be avoided.
Not taking all the work into account. This is a common problem, especially with earlier, high-level estimates. You may just miss some major work that you did not understand to be a part of the project, such as documentation or training. Typically, however, you underestimate the size of deliverables that need to be completed or you do not include all of the activities required to complete the deliverable.
Wishful Thinking. Anyone that has provided estimates of work knows that there can be pressure from your client to make the estimate as low as possible. Ultimately, the client wants to get what they need for as little effort (and cost) as possible. In many cases, there is a tendency on the part of the estimator to get caught up in that mindset as well. The estimator ends up “wishing” the work ends up within the client expectations.
Committing to best-case scenario. The client wants it done as quickly as possible. Your manager wants it done as quickly as possible. You think it can be done quickly. However, you get into trouble because you think about what it would take to complete the work if everything went right. You might even think in terms of a range of effort for the work, but then too often you end up committing to an estimate at the lower, or optimistic, end of the range
Assuming higher quality work than can deliver. This problem includes estimating based on building at a certain level of quality the first time. However, as the project is executed, you realize that your ability to build to a high level of quality the first time is limited, resulting in overages for rework, bug fixes, retesting, etc.
Committing based on available budget. In this case, the client has a fixed amount for the budget. The project manager thinks there is a chance he or she can get it done within available budget, so he or she commits based on that number. This is similar to the best case scenario problem above.
Not recognizing estimating biases. Estimating biases sneak into estimates all of the time. Some are optimistic biases and some are pessimistic biases. Optimistic biases will result in underestimating the work and can include:
Tending to think the work is simple.
Tending to think your team can accomplish more than they really can.
Not taking into account project risks, issues, miscommunications, etc.
Tending to be optimistic in the first place.
Pessimistic biases will result in overestimating the work and can include:
Overestimating the work because you had a bad experience on a similar project in the past.
Overestimating because you don’t really want to do the work. You estimate high and hope the project will be cancelled.
Tending to be pessimistic to begin with.
Your biases are always there. The key is to recognize the
biases and counter the biases where you see them. This will help you prepare
estimates that are as valid as possible.
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