Using Survey Groups within the MTurk Toolkit is a way to ensure unique workers across multiple studies that are simultaneously live and collecting data.
If you plan to run multiple studies at the same time and you want to ensure that workers cannot participate in more than one of those studies, you can use the Survey Groups tool. Survey Groups work by grouping a set of your studies together, and then when those studies are Live at the same time, ensuring that workers can only take one study within the group. Simply using the Exclude Workers tool will not accomplish the same objective because the Exclude Workers tool only excludes workers once they have been approved or rejected in previous studies.
When you use Survey Groups, any worker who accepts a study in the group will be disqualified from accepting other studies in that group. Using this tool, your studies are guaranteed to have a mutually exclusive group of respondents. To read more about this tool see our blog or this article for information about how to create a Survey Group.