Semi-structured interviews usually last about an hour, so unless your questions require only brief answers, that will set a limit on how many questions you can ask.

The difference between structured interviews and semi-structured ones is that a researcher wanders off the question form in the latter to enrich data. Therefore, finding the needed answers should limit the number of questions, bearing in mind that redundancy and question rewording could reduce data richness. That said, I agree that a semi-structured interview should not exceed 60 minutes. Here is a helpful read.

Kallio, H., Pietilä, A.-M., Johnson, M., & Kangasniemi, M. (2016). Systematic methodological review: Developing a framework for a qualitative semi-structured interview guide. Journal of Advanced Nursing, 72(12), 2954–2965. https://doi.org/10.1111/jan.13031

Good luck,

Merajsadat Malakouti The variety of questions that can be included in a semi-structured interview for a qualitative inquiry is not strictly limited. The number of questions will be determined by a number of criteria, including the study's unique research aims and objectives, the complexity of the topics under consideration, the depth of analysis needed, and the size and diversity of the sample.

In general, it is critical to find a balance between getting enough material to answer the research objectives and without overloading the respondent with inquiries. A semi-structured interview provides for more freedom and allows the interviewer to go further into issues, but it is still critical to have a clear objective and avoid asking too many unrelated or repeated questions.

Before performing the main research, it is also a good idea to pilot test the interview guide with a small number of participants to confirm that the questions are clear, relevant, and suitable, and to make any required revisions.

Overall, while deciding the number of questions to include in your semi-structured interview, keep your study's particular objectives and aims in mind.

Semi- structured interviews usually give you the liberty to add probe questions if you feel a particular response by the participant requires greater elaboration. So keeping the primary interview schedule short is beneficial with simply worded, short questions. Usually an interview lasting 45-55 minutes will be most helpful after which your participant may feel less inclined to respond and get tired of it.

Semi-structured interviews make coding easier, giving you a consistent, structured map as you process the data. But an interview is not a survey. The trickiest part, in my opinion, is listening... REALLY listening. Asking a question to obtain information already given 10 minutes before induces the feeling that the interviewer is not listening, which can induce a reluctance to answer frankly. The semi-structured approach should allow the respondent space to respond and add unsolicited information if desired. This should be taken into account if you plan to ask many questions.

Nazneen Mogrelia If a typical semi-structured interview lasts 60 minutes, then 15 questions amounts to 4 minutes per question without any probing. I myself would say that anything with over 11 questions more structured than semi-structured.

I completely agree with @David L. Morgan. I usually design 4 topic-related "leading questions" that address the main perspectives I want to explore in a for one-hour planned interview. Each of these questions can be assigned some key words, of course. In my experience, anything beyond that will tend to hinder a deep, open conversation.

Merajsadat Malakouti Semi-structured interviews are based on questions that work like "guide for the discussion". So, for getting response about 3 areas of discussion, there can be 3-4 questions per theme. So, around 10-12 questions maybe okay.

There is no set number of questions for a semi-structured interview. The number of questions depends on the research question and the goals of the study. The goal of a semi-structured interview is to allow the interviewer to ask open-ended questions while still maintaining some control over the interview process. This allows for flexibility in the interview process while still ensuring that the research question is addressed.