Analogous estimating, also called top-down estimating, is a form of expert judgment. With this technique, you will use the actual duration of a similar activity completed on a previous project to determine the duration of the current activity—provided the information was documented and stored with the project information on the previous project. This technique is most useful when the previous activities you're comparing are similar to the activity you're estimating and don't just appear to be similar. And you want the folks who are working on the estimate to have experience with these activities so they can provide reasonable estimates. This technique is especially helpful when detailed information about the project is not available, such as in the early phases of the project.
Top-down estimating techniques are also used to estimate total project duration, particularly when you have a limited amount of information about the project. The best way to think about top-down techniques is to look at the estimate as a whole. Think about being on a mountaintop where you can see the whole picture as one rather than all the individual items that make up the picture.
For instance, let's return to the house-painting example. You would compare a previous house-painting project to the current house-painting project, where the houses are of similar size and the paint you're using is the same quality. You can use the first house-painting project to estimate the project duration for the second house-painting project because of the similarities in the project.
Top-down techniques are useful when you're early in the project Planning processes and are just beginning to flesh out all the details of the project. Sometimes during the project selection process, the selection committee might want an idea of the project's duration. You can derive a project estimate at this stage by using top-down techniques.
Was this article helpful?
What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.