Analogous estimation, also known as top-down estimation, is a project management technique that uses historical data from similar projects to make an estimate for the current project. This approach involves identifying a previous project that is similar in scope, size, and complexity to the project is estimated, and then using the data from that project to make an estimate for the current project.
Analogous estimation is useful in situations where there is limited information available about the project, and when it is difficult to break down the project into smaller tasks or activities. It is also useful when there are tight deadlines or limited resources, and when the project is similar to previous projects that have been completed.
An example of Analogous estimation would be a software development company that needs to estimate the time and cost of developing a new mobile application. They identify a similar application that was developed by the same company in the past, and use the data from that project (e.g., duration, cost, number of development hours) to make an estimate for the new project.
However, analogous estimation also has its own limitations as it heavily depends on the similarity of the project, the data available and can be affected by external factors that have changed from the previous project.