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What Estimations are Required During Planning?
A successful project plan will include information on the budget, resources, task duration and when the project will be completed. You will want to perform estimates shortly after completing a breakdown of tasks and milestones. If the estimation process begins too soon, there won't be enough information. If estimation is undertaken too late, then corrections become more difficult to make.
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How do you Estimate Time?
Estimating time accurately is one of the harder tasks in project planning. It takes experience to know how long particular tasks will take within a project. Underestimating the duration of projects and tasks is far more common than overestimating durations. One reason for this is that project managers take into account how long it might take them to complete a particular task, but overlook that this task may take longer for someone else – or that some unfortunate event may occur.
To estimate time accurately, it helps if you have already decomposed your project into the smallest possible components. You may have no idea how long it will take to complete a new database program, but you might have an idea of how long it takes to do component parts. By breaking things down this way, you can create a more accurate estimate.
Project managers also have to account for potential delays in their projects. By adding in some “padding time” for those unexpected events that do arise during the project management phase, you can account for these. Overestimating time is far better than underestimating time needed on a project.
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How do you Estimate Resources?
Once an accurate time-estimate has been generated, you can estimate how many and which resources will be required for project completion. You will most likely require both human resources and physical resources (for example, if you are putting together an animation, you will need both animators and animation software). Estimating the physical resources is relatively simple – look at the task list and ask yourself if you require anything aside from a person to complete the task.
Estimating human resource requirements is a bit trickier. One way to do this is after taking into account any specialists you will require, tally up the total number of hours you have estimated for the project duration. Divide this number by the number of weeks you have scheduled for the project. Divide this by forty to determine an estimate of how many human resources you will require for your team.
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How do you Estimate Cost?
Cost estimations depend upon accurate estimations of time and resources. There are various methods for estimating cost – analogy (looking at similar projects), parametric (derived from a mathematical formula) or bottom-up (adding up the costs of all the parts to obtain the cost of the whole, etc. What is important is that the method used for estimating project cost produces an accurate result. Nothing is worse than estimating a project will cost $25,000 to complete and finding out that it actually costs $60,000 to complete. Go over your figures once, and then go over your figures a second time.
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For more information on estimation and estimation methods, you may wish to read the following Bright Hub articles:
"Decomposition and Bottom-Up Estimation" by Ronda Roberts
"PERT Formula Series" by Ronda Roberts
"Resource Management in Software Project Management" by Chemuturi
"Project Success using Scrum Story Points" by mistyfaucheux