Common Estimating Mistakes

Common Estimating Mistakes

The project manager and project team are responsible for developing good cost and schedule estimates for the work of the project. This can be difficult without historical data to reference. Here is our top ten list of the most common estimating mistakes.

1. Failure to account for reasonable risks in the estimate. There are reasonable and unreasonable risks. A good estimate should account for the most likely risks and adjust the estimate accordingly.

2.  Allowing external pressures from sponsors or management to dictate unrealistic targets that are not supportable.

3.  Failure to breakdown work efforts into small enough units to be estimated well.  Or failure to clearly define the work effort in enough detail that it can be estimated with any precision.

4.  Errors and omissions such as mathematical errors introduced into the estimate or omissions in specific (cost) categories that should have been included in the estimate.

5.  Document and validate all estimating assumptions given to you by a third party... especially if it is provided by someone non-technical such as the customer.

6.  Attempting to estimate someone else's work who has different skills and competencies than yourself.

7.  Optimistic estimating bias which leads to underestimating the amount of effort it will actually take to complete the work defined.

8.  Rushing through the estimating process and not giving it the attention and consideration due.  An estimate provided in a hurry is a poor estimate.

9.  Failure to document the basis of the estimate which provides the framework and reasoning for the estimate. For example, the drive to the office will take longer during rush hour traffic than at off peak time periods.

10.  Playing the estimating game.  Estimators pad their estimates knowing that management will shave any estimate given on the assumption that padding has been added or to provide the implementers with "stretch goals".

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