The number and  depends on  research objectives, types of questions (closed, multiple-choice, open) and the considered budget.

A good questionnaire is one which help directly achieve the research objectives, provides complete and accurate information; is easy for both interviewers and respondents to complete, is so designed as to make sound analysis and interpretation possible. For online surveys the attached article suggests the the time taken to respond should be less than 20 minutes and after that fatigue becomes pronounces and shorter surveys results in more quality responses. 

The attached links discuss the design of a good questionnaire.

http://en.wikipedia.org/wiki/Questionnaire_construction

http://www.surveysampling.com/ssi-media/Corporate/white_papers/SSI_QuestionLength_WP.image

http://www.lboro.ac.uk/media/wwwlboroacuk/content/library/downloads/advicesheets/questionnaire.pdf

The whole issue depends on the scope of the research. There is no fixed number of questions. 

Dear @Gopinath, this is a fundamental question; the number of questions that are sufficient in a questionnaire method to good Ph.D. Research work depends on the study, the field, and the budget of the study. It should also be compared to similar studies in the field and trying to surpass previous and existing studies.

The number and  depends on  research objectives, types of questions (closed, multiple-choice, open) and the considered budget.

A good questionnaire is one which help directly achieve the research objectives, provides complete and accurate information; is easy for both interviewers and respondents to complete, is so designed as to make sound analysis and interpretation possible. For online surveys the attached article suggests the the time taken to respond should be less than 20 minutes and after that fatigue becomes pronounces and shorter surveys results in more quality responses. 

The attached links discuss the design of a good questionnaire.

http://en.wikipedia.org/wiki/Questionnaire_construction

http://www.surveysampling.com/ssi-media/Corporate/white_papers/SSI_QuestionLength_WP.image

http://www.lboro.ac.uk/media/wwwlboroacuk/content/library/downloads/advicesheets/questionnaire.pdf

Dear Gopinath

You cannot have a theoretical maximum or minimum number of questions in a survey. You need to decide that based on the actual topic in question and the hypotheses that you want to prove. As our dear friend Behrouz said the smaller the better for the responses. Keep that in mind, and also need to supplement your surveys with other options such as interviews.

You need an hypothesis to test, the confidence required and then perform a statistical power analysis to determine how many data samples to collect.

There should not be more than 50 items on your questionnaire or you risk fatigue of survey respondents. Too many questions means people will quit the survey before they complete all questions. For more than 50 items, you will need an incentive to bribe people to complete the survey. 

All you need response from user

 One page is good enough but if incentive given can go 2 to 3 a4 pages

I am yet to start my PHD but this what I think. I stand to be corrected.  The length of a questionnaire should depend on the type of research (i.e. qualitative, quantitative) you are doing and the method you want to use. For instance if you are using a mixed method you question may be based on only the qualitative aspect on your work. Your questions will then bother on the variable and invariable factors you want to consider and the items you want to test. In this regard one to two pages should be a meaningful questionnaire.

one-two pages would be fair enough......

We live in a world in which many humans are in a "hurry-up" state. A lengthy questionnaire is not tolerated by those who will answer it especially if the questions are too deep & each question exceeds 2 lines. I have been a "target" of questionnaires for students doing research for the master degree in education several times.

If the questionnaire is 3-4 pages, I usually finish it in less than half an hour. If it is more than that, I tell the researcher to come tomorrow.

Since the question is about PhD research work, then 5 pages with 50 questions distributed equally & displayed well in clear straight language, may be adequate. If there is need for more questions & to double check the answers, I see no harm in preparing more than one questionnaire but they ought to be given to the respondents when they are not busy.

Completing a thesis questionnaire can help you prepare your project and it is one of the effective methods of thesis research. Your thesis questionnaire should be planned in order to get accurate results. You should decide on the participants of your questionnaire and prepare all your questions to be clear and precise.

There is no upper or lower limits for questions sufficient in a questionnaire method to good Ph.D. Research work. This depends on many variables, such as, the research nature, the subject of the research, and the variables.

I do agree with all contributors that no such hard rule exists. It really depends on the phenomena to be investigated  and the skill of the PhD researcher.

It is difficult to answer because it depends on the subject and on the means employed. In my opinion if the study contains a main question and two secondary questions with solid methology to permit at the end of the study to conclude; that's fine.

It definitely depends upon the type of research work. The main objective should be in what way the output of research work is going to serve the need and the problem of society.

I do not quite understand the question!. What type of questions we are talking about? Do you mean questions in an oral examination of a PhD student? If this is what you mean I think there is no specific number of questions. I thing the questions should cover the important point of the material at hand.

I believe there are no fast rules to the number of questions to be asked in a questionnaire. However, there is need to ensure that questions easily give answers to the research questions or hypothesis to be proven. 

As far as the number of questions you decide to ask, can help you achieve your objectives totally, then that number is alright.

i am pursuing Phd, what i feel that questionnaire should be according the scope and objective of the thesis but , i should try to keep the questionnaire not so lengthy becoz no one will ready to answer the question, as people are so busy and without any benefit no one will ready to give time, it should be comfort zone.

Dear Sir, I strongly agree with the earlier recommendation and suggestions. the Number does not matter and there is no rule of thumb for the number of questions in the questionnaire . It all depends on the nature, objective and the information one is seeking to achieve during the study. At the end, it should answer the objectives. Best regards.

Dear Sir, I strongly agree with the earlier recommendation and suggestions. the Number does not matter and there is no rule of thumb for the number of questions in the questionnaire . It all depends on the nature, objective and the information one is seeking to achieve during the study. At the end, it should answer the objectives. Best regards.

5 or less than 10. Number of finger.

Malhotra et. al. (2013), suggest a minimum number of 150 respondents in order to test the hypotheses developed.