# Usability Testing of Mobile Applications:
## 4 Methodological Framework for Mobile Usability Testing
### Data Collection Techniques
#### 4.2.4 Interview  
An interview is a qualitative research method that relies on asking people questions in order to collect primary data that are not available through other research methods. Typically, a researcher engages in direct conversation with individuals to gather information about their attitudes, behaviors, experiences, opinions, or any other type of information. In the course of such a procedure, three different approaches can be applied [117]:  
* An unstructured or non-directive interview is an interview in which the questions are not predetermined, i.e., the interviewer asks open-ended questions and relies on the freely given answers of the participants. This approach therefore offers both parties (interviewer and interviewee) flexibility and freedom in planning, conducting, and organizing the interview content and questions [118].
* A semi-structured interview combines a predetermined set of open-ended questions, which also encourage discussion, with the opportunity for the interviewer to explore particular issues or responses further. The rigidity of its structure can be varied depending on the purpose of the study and the research questions. The main advantages are that the semi-structured interview method has been found to be successful in enabling reciprocity between the interviewer and the participant [119], allowing the interviewer to improvise follow-up questions based on the participant's responses. The semi-structured format is the most commonly used interview technique in qualitative research [120].
* A structured interview is a systematic approach to interviewing in which you pose the same pre-defined questions to all participants in the same order and rate them using a standardized scoring system. In research, structured interviews are usually quantitative in nature. Structured interviews are easy to replicate because they use a fixed set of closed-ended questions that are easy to quantify and thus test for reliability [121]. However, this form of interview is not flexible; i.e., new questions cannot be asked off the cuff (during the interview) as an interview schedule must be followed.  
In usability studies, unstructured interviews can be particularly useful in the early stages of mobile application development by identifying the pros and cons of graphical user interface design [122]. More generally, an unstructured interview can be used to elicit as many experiential statements as possible from a user after testing a product [123]. In addition, this method has been widely used to gather non-functional requirements, especially those that fall within the scope of usability [124].  
A semi-structured interview format, which also relies on asking a series of open-ended questions, is said to elicit unbiased responses with the aim of uncovering usability issues by providing detailed qualitative data [125]. In practice, semi-structured interviews are used as a follow-up method, conducted either face-to-face or by email. It seems to be a widely accepted practice in the usability testing of mobile applications to combine both closed and open questions [126].  
A structured interview is essentially the administration of a questionnaire, which ensures consistency and thoroughness [127]. The obvious advantage of a questionnaire is that it can be completed by the participant on paper or electronically, allowing relatively large samples of data to be collected with relatively little effort on the part of the experimenter, whereas disadvantages include inflexibility and the inability to pursue interesting lines of inquiry or to follow up on responses that may be unclear. However, the structured nature of such instruments allows them to be replicated across the research community, while testing their reliability and validity on different samples demonstrates their degree of generalizability.  
It is worth noting that [PERSON] and [PERSON] [128] provide a comprehensive overview of existing interview types, as well as useful guidelines for developing and conducting each one.