Lesson 1, Topic 1
In Progress

Improving time estimates


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Even with all the historical problems and disruptions that have been caused by poor activity / task time estimation, most existing material provides little more than a cursory coverage of how project planners and managers can come to grips with the practical aspects of time estimation.

In reality, a combination of variations from estimates and failure of management to adhere to the original time estimates, even if they had been reasonable, create and perpetuate the project management myth that all project estimates will be inaccurate and all projects will eventually slip. The material presented in this topic will provide you with some perspectives. The approach of dividing the time estimate into estimate and prediction elements will hopefully be a way of incorporating quantitative technical and intuitive input.

It is suggested that there are six methods for estimating or to improve activity duration:

  • Similarity to other activities – the use of previous experience on the same or similar projects.
  • Historical data – the use of captured data from other projects and other sources from ‘lessons learned’ and this will help to improve the organisational maturity.
  • Expert advice – access from external experts such as vendors, suppliers, contractors, sub- contractors etc.
  • Delphi technique – this is a group technique that accesses the group knowledge to arrive at an estimate, tabulated and reviewed by the group, either collectively or individually. Discussions lead to a refinement of the estimates and consensus can be reached by using averages of remaining estimates.
  • Three-point technique – this is discussed in greater detail below. It involves nominating optimistic, realistic, and pessimistic guesses and weighting the estimates to achieve a final figure. There is a statistical basis for the approach but that is not covered in this course.
  • Wide-band Delphi technique – this combines the Delphi and the three-point techniques using an expert panel.

The other alternatives suggest the following seven guidelines for preparing estimates for times, costs and resources:

  • Responsibility – at the work package level, estimates should be made by the person most familiar with the task.
  • Use several people to prepare the estimates as they will have a better chance of being reasonable and realistic when several people with experience and knowledge are involved.
  • Normal conditions – estimates are normally based on assumptions and they should be based on normal conditions, efficient methods, and a normal level of resources.
  • Time units – specific and relevant units of time should be selected early in the estimating process, such as work days or hours depending on the time frame and scale of project.
  • Independence – treat tasks as independent of other tasks to avoid seeing the chain of tasks as a single time frame and then breaking the individual tasks down to fit into it.
  • Contingencies – work package estimates should not include allowances for contingencies, and should allow for normal conditions and circumstances. Contingencies are best managed at higher levels by the project manager or sponsor.
  • Adding risk assessment to the estimate helps to avoid surprises to stakeholders – consider identifying a range of estimates to highlight tasks with higher risk factors. This is not work package estimates but rather a higher-level risk management.

Frequently experiencing issues are the practical aspects of time estimation. Lack of details and the format of the data in PM software can give a false feeling of confidence which has no factual basis.

  • Use of ‘common sense’ expectations
  • Do not be too optimistic, excited, or pride, resulting with over-committing yourself.
  • Break task down to obtain better visibility of the likely problems.
  • Pay attention to trouble spots with careful planning.
  • Provide some in-built buffer, where appropriate. Do not Abuse!
  • fair and reasonable’ when negotiating time with the performing person or group.
  • Prioritise the project vis-à-vis other projects and the organisation.

Figure 3-4 illustrates the major components in determining time estimates through participation.

FIGURE 3-4: TIME ESTIMATES THROUGH PARTICIPATION – TYPICAL