It is important to remember that you don’t have to please every thesis/dissertation chairperson and committee member. Many committee members have philosophical and technical differences of opinion. It is important for you to avoid getting in the middle of any verbal combat among committee members. There will be times when you must arbitrate to gain consensus, and there also will be times when you must stand up and assert your own views to the committee. Intellectual disagreement is inevitable, but your points and ideas can succeed when you convey them tactfully and respectfully to improve your position and credibility with the committee.
Always project a professional image. The best course of action would be to dress like one of them, talk like they do, and write like they do. This will help you because you are no longer presenting the image of a student. You want faculty to perceive you as one of them even though you are not quite there yet.
As a dissertation student, you have much to gain by realizing that you need to become empowered. What I mean is: you need to realize that all dissertations will have limits. All dissertations will have weaknesses, and there’s nothing wrong with that, especially if they cannot be overcome. Acknowledge the weaknesses. Now certainly, if the weakness could be controlled or eliminated, then you need to do so. However, all research and all dissertations have some limits and weaknesses. You must acknowledge those and not be afraid. If a faculty member becomes critical of your design, you can take some time to seriously consider the criticism. There is no perfect response. For instance, one appropriate way to respond by saying that your dissertation needed to be limited and that’s why you kept the number of participants to just a few. When possible, locate another study or source that supports your position. This way the literature sort of becomes your defense or justification for how you have created your design.