What you're supposed to do in a defense:
- Defend the choices that you made in conducting the research -- know /why/ you did what you did. Understand the weaknesses of your choices, and be open to considering some of the suggestions posed by the examiners.
- Be critical, and be ready to think and reflect on the comments that you hear.
- There are some questions that examiners have an answer in their head about. In other cases, they really don't.
So, to me there are three types of questions:
- [Clarification] I don't understand X. Can you explain it in further detail?
- [Justification] Explain/justify the choice of X.
- [Speculation] What would you do next on this project?
You can cross this with any of the major sections of your paper (e.g. Problem, Motivation, Approach, Implementation, Discussion, Conclusion) to get a sense for what the questions might be like. For example:
- Clarification/Problem: I don't understand how this visualization works. Can you explain it to me again?
- Justification/Approach: Why did you convert mood into an ordinal (numerical) scale? Was this the right choice to make? How could you have done it differently?
- Speculation/Problem: Would you expect this data collection to happen automatically in the future? How would the results you got differ if you'd collected a different kind of data? Is this the best type of visualization for this data? How might you change it?