Common scenario and situation leading to similar questionnaire -- Is it plagiarism? I recently had to make a questionnaire for my research. For this questionnaire, I tried taking some ideas from other examples for the questions. Another student was working on the same topic and did her questionnaire before mine, but didn't publish any results yet. After comparing my questionnaire with hers, it was clear that some questions are a remarkably similar, due to covering the same topic, same country, same society and same climate. The other student made a complaint that I have copied some of the questions from her questionnaire. 

Could anyone please help me know whether did I commit plagiarism? How should I deal with the present situation?
tried to obtain some ideas from other examples for the questions


That has the hallmark signs of plagiarism, although without seeing the original sources and your questionnaire it is hard to give a definitive answer. It is okay to look at other sources for ideas. Paraphrasing is okay also. Copying, or even changing a few words, is not okay without proper attribution. In general it is okay, and often desirable, to reuse an existing questionnaire, or parts of an existing questionnaire, in a new study, but you need to provide attribution to the original questionnaire.

As to the similarity between you and the other student, this depends on if you used her questionnaire for ideas. If you never saw her questionnaire, then you clearly did not plagiarize from her. It is possible that both of you got ideas from the same source, in which case you both plagiarized someone else.

You need to determine if you plagiarized and if you did plagiarize, who you plagiarized from. If you plagiarized from the student, you need to tell her and your supervisor. If you plagiarized from a third party, you need to tell your supervisor. You should also inform the student that your questionnaire contains plagiarism, but that you did not plagiarize her. You should also tell her that you are telling your supervisor.