Question

discuss eight Tools and Techniques of time estimation with examples.

Answer 1

Tools and techniques for time estimation

• Bottom-Up-Estimating

Bottom-Up-Estimating enables us to create an estimate for the project as a whole. In order to analyse from the "bottom-up," break larger tasks down into smaller detailed tasks, and then estimate the time required to complete each one. Since each task is considered incrementally, the estimate of the time required is likely to be more accurate. The total amount of the specific tasks can then be added to obtain the total amount of time needed to complete the plan.

e.g. On a simple note, if a project has three tasks A,B and C. If Task A takes 1 week, Task B takes 3 weeks and Task C takes 6 weeks, then the total completions time of the project will be an addition of the three task durations which will be 10 weeks.

• Top-Down Estimating

In top-down analysis, an overview of the expected timeline is developed first by using past projects or previous experience as a reference point. It is often helpful to compare top-down estimates against the bottom-down estimates to ensure accuracy

Both of the above techniques work well together. It must be noted that the bottom-up estimates might not be wrong if they differ widely from the top-down ones. In fact, it is more likely that the opposite is true. Instead, the top-down estimates should be used to challenge the validity of the bottom-up estimates and to refine them as appropriate.

• Comparative Estimating

In comparative testing, we simply look at the time it took to complete similar tasks on other projects. This method is only useful if the analogy is valid and the available information would then need to be scaled up or down to meet the needs of the current project being estimated.

• Parametric Estimating

With this method, the time required to produce one deliverable is estimated and then it is multiplied by the total number of deliverables required.

For example, if we need to create pages for a website, we first estimate the time required to create one page and den multiply this time by the total number of pages to be produced. For instance, if 1 page takes 1 minute then 100 pages will require 100 minutes to complete

• PERT (Program Evaluation and Review Technique) or Three Point Estimation

PERT technique was derived by the U.S. Navy, where it was used to estimate the time taken to develop ballistic missiles. It was a huge and complex project but thanks to PERT, the project ended two years earlier than expected.

PERT functions by managing probabilities. It takes into consideration the optimistic time (when all favourable things happen, the pessimistic time (when all unfavourable things happen) and most likely time (when both favourable and unfavourable things happen). Pert uses this three-point analysis to estimate time.

For example - If you are using a vehicle to reach from one point in the city to another, the optimistic time taken is 30 mins, pessimistic time is 90 mins and the most likely time will be 60 mins. So, the range in which the travel time will fall is 30 mins to 90 mins

• Expert Opinion

In most cases, an internal or external expert's help will be required to estimate the work to be completed. The expert does this mainly by benchmarking with other companies in the industry and estimating a probable timeline.

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