Tag questions and hedges

In chapter 10, Coopman talks about using language effectively. In the section about language and gender, he talks about powerless language. He uses speech jargon in identifying concepts such as tag questions and hedges. I have never heard of these concepts but I understand when he connects them to an uncertain way of speaking. However, it bugs me that although he references his evidence for his assertions on gender, they are obviously based on some type of survey or statistic which I cant take as a fact. I do think it is important that he talks about these concepts because it can help us as public speakers identify possible red flag phrases that we never thought may contradict from our speeches.