Group Questions, also known as Evaluation Sets, are a set of questions that apply to more than one item. For example, there could be group questions surrounding a set of cars or commercials. Responses to one question related to the responses to the other questions. For this reason they are treated differently, and questions belonging to one group cannot be run in the same tab as questions from any other group.
Group Question Usage
You can usually identify a group question by the (G1) or (DG2) or similar identifier after the text of a question. A (G1) or (DG1) would indicate that it is part of Group 1 for that database. Not many databases have group questions and even fewer have more than one. If there is more than one, you should see a (G2) and possibly (DG2) as well and so on. The (DG1) tag, in addition to indicating that the question is part of group 1, also indicates that it is the dominant question. Dominant questions are best used in the column. They are the sets of cars or commercials for which each of the regular group questions are asked. If a group does not have a question with the dominant group tag, it may just be the first question in the group, or it may be that the group does not have a dominant question.
Go to Filter Logic for information on filtering group questions.