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Longitudinal studies This is a research design that involves collecting data on cases on several occasions over an extended period.


The degree to which different observers, researchers etc. (or the same observers etc. on different occasions) make the same observations or collect the same data about the same object of study. The concept is highly contentious in qualitative research where it is often not clear what the same object of study is.


The extent to which an account accurately represents the social phenomena to which it refers. In realist research it refers to the degree to which the research provides a true picture of the situation and/or people being studied and is often referred to as internal validity. Postmodernists, who contest that research can ever provide a single true picture of the world contest the very possibility of validity.

For more information generally on the quality of qualitative research see,

Book iconFlick, U. (2007) Managing Quality in Qualitative Research. London: Sage.

Book iconSeale, C.F. (1999) The Quality of Qualitative Research. London: Sage.

interviewsThe interview structure


Authors of this page:Dawn Clarke and Graham R. Gibbs

Affiliation: University of Huddersfield

Date written: 27th July 2008






Learning outcomes


Frances decided that there should be two parts to the study. The first was the interviews with the patients the second was those with the GPs. She left the interviews with the GPs till she had completed the first set of interviews with patients.


Loudspeaker iconFrances explained this decision:

I didn’t see the GPs until the second interview stage with the patients because I wanted to see what was coming out of the patients' [interviews] because that might influence the sort of questions [she asked the GPs], all the prompts and things that might be asked but in fact I don’t think it did make such a big difference but that was the idea.


Based partly on her experience, Frances decided on a long time period for the series of interview. She knew that the effects of the injuries needed time to become evident therefore, she chose a longitudinal approach for her design. This involved speaking to respondents on three occasions over a time period well beyond the normal whiplash injury recovery time. She decided to undertake three interviews with each patient respondent: the first between three weeks and three months after the accident, the second 3 months later and the last a year after the accident.


Loudspeaker iconHear Frances explain this time period was needed.

The interviews were three in-depth interviews which the structure was the same for, the first one was three-weeks and beyond after the accidents, I wanted to rule out what would be a normal recovery phase so that can be out of the way and then from there, they [the participants who had experienced whiplash] were seen three months after the first interview.


In the first interview respondents talked about the accident itself as well as their experience afterwards. In the later interviews Frances repeated the questions and topics about their experience. She used the same interview schedules with all respondents.


Loudspeaker iconHear Frances talk about the schedule.

The only difference in the interview schedule was the actual accident itself and the experience, that part was, was taken out but otherwise it [the next two interviews] followed the same [structure]. So that was the idea behind that, how are things? Any changes?


This gave some reliability and validity to the study. Frances knew that if she detected differences between respondents or within respondents over time then these differences were likely to be real changes in what the respondents had experienced or real difference between them rather than the result simply of having talked about different things in each interview.

Frances could explore the effects of the injury over a period of time by comparing the results from the different interviews with the same respondent.

However, as she undertook the first two rounds of interviews, Frances realised that there needed to be a slightly different emphasis to the final interview.


Loudspeaker iconFrances explained this change of emphasis:  

And then there was a final interview a year later at which point they were asked again a similar thing but it was more emphasis about... if somebody came to you with a whiplash injury what advice would you give them? I think that’s important if we’re looking at patient’s experience and wanting to utilise that in terms of changing practice then it [the interview] needs to be open and allow them [the participants experiences] to come through.


it is one of the strengths of qualitative research that the research design does not need to be kept fixed over the period of data collection. Researchers often change what they are investigating to reflect what they have learned in the earlier part of the study. In the case of Frances' study there were points at which the detail was changed and re-defined to enable her to obtain the data she needed.

Moreover, because of the time between each round of interviews Frances had time to transcribe the first set and was able to give the participants a copy before the next interview. This gave her an extra lever in finding out about what, if anything, had changed for the patients. She used these transcript as a way of reminding respondents about what they had experienced soon after the accident.


Loudspeaker iconFrances explains the use of the transcripts:

There were two things behind that. One was that it [the transcript] was a reminder of what had taken place at the previous interview and also they [the participants] had an opportunity to say about something that they’d said, but importantly it wasn’t about the interview themselves, it was about looking at what changes might have taken place between the interviews.  And one of the things I wanted to capture was how this injury for them changed over time, how it affected them over time.  Most of the research is retrospective and so it looks at what happened before rather than following through how this [injury] actually impacted on them or not.


Frances, from her own experience, was aware of the probable long term nature of the injury and therefore understood that she needed to develop an interview schedule accordingly. Furthermore she understood through her literature review that there was very little previous research that was prospective, in other words that looked forwards and followed the effects of the injury as they were happening. Taking these factors into consideration Frances believed that a single interview with each respondent would not have yielded relevant data. It would, at best, have produced retrospective data that focused on the accident and its immediate impacts which meant the research would not have been able to produce innovative results.


Loudspeaker iconFrances explains how her data took her understanding beyond the conventional picture:

And I think that what it [the data set] does show is that actually underneath, the kind of injury that’s played out at home on their [the participants'] every day life, actually, the kind of idea of it just being a minor injury, classified as such, actually doesn’t really take into account, or even recognise and acknowledge that actually for some people it’s much, much more than that and they have to learn ways of actually accommodating and managing that themselves in a sense.


By asking the right questions and being open to all kinds of responses, researchers can discover things that others have not realised and even hear things that respondents have said to no-one else.


Loudspeaker iconFrances talked about one such experience with one of her respondents:

I think possibly because of the way the interview guide was structured, the questions were structured, that he [the participant] was able to talk about his experience of how it affected him with his driving or how it affected him at work, you know, what his fears were, or his uncertainties were, in a way that possibly he wouldn’t have spoken with other people.


The detailed activities undertaken in a qualitative research project don't always follow, or even always need to follow what was originally planned. Frances found that as she developed her views about the nature of the experience of whiplash injury, she needed to change both the kinds of questions she asked and the sort of interview design she used. This flexibility in research design can be seen as one of the strengths of qualitative research since the issues that need addressing may not be evident from the onset. It also means that sometimes adjustments needed to deal with problems actually result in a much better project. In Frances' case she was surprised how long it took to access willing participants and indeed how few of them there were. Her response was to use a longitudinal design for the interviews and this allowed her to gather more data about the longer term effects of the whiplash injuries.


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The resources on this site by Graham R Gibbs, Dawn Clarke, Celia Taylor, Christina Silver and Ann Lewins are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.



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