Yadmin is the yaacs's GUI dedicated to perform the main adminstrative CATI statistic tasks.
You can use it to manage surveys' sampling, quota checking and to configure all survey process's parameters.
During the survey process you can easly monitor all its aspect (e.g. how many interviews has been completed, how many contacts has been used) and you also have a quick look at your operators' performance.
You can tune parameters setted at project creation time "on the fly" to be able to adjust them as needed.
When a project will be finished you can use yadmin to get some data about operators, such as how many hours each of them has spent on it (very usefull for your billing stuff) and so on.
To learn more about yadmin be sure to check out its documentation on the docs section.