The researchers used a structured interview. Structured interviews have an interview schedule that asks specific questions and is not open to taking in other information. The aim of this approach is to ensure that each interview is presented with exactly the same questions in the same order.  Questions tend to be less open-ended and allow for easier comparison than in an unstructured interview. The method is less "natural" than unstructured interviews and is often seen as having lower ecological validity.

The researchers interviewed volunteers who were available at a cancer screening center. This was a sample of opportunity.  It was also from five different locations in Sweden, theoretically providing for a more diverse sample. This sample could also be considered a haphazard sample as it was made up of people who stopped by the mobile screening center. The majority of the sample was middle-aged and female.

There are a few alternatives to this method.  They could use a focus group in which people share their thoughts in a group setting.  This may prompt ideas that were not shared in a one-on-one interview.  Focus groups also have higher ecological validity. The researcher could also do a case study, looking at the participants' actual habits of a summer season and comparing that to their perceptions of their behaviour. This would be more holistic and would control for biases of the participants in an interview situation.

The researchers would have to gain consent from the participants in which they would have to explain the nature of the interview and the goals of the research.  They may decide not to tell the true aim of the study until the participants are debriefed. This would be deception of omission, with the goal of not letting the participants know that they are trying to find out if they are overly optimistic about their risks of skin cancer.  In the debriefing, the researchers would have to explain how the data would be used and that the participants' identities would remain anonymous. In addition to their names being anonymous, it would be important that the date of the interview and the place where the interviews occurred would not be revealed.  Keeping the data anonymous protects the interviewees from potential embarrassment. They would also share the findings with the participants with the hope of changing health behaviours. The participants have the right to withdraw at any point in the study - for example, if they do not like the questions or feel uncomfortable with the questions being asked. They may also withdraw once they learn of the results of the study.  This may have an influence on the study as those people who felt the most "judged" could pull out of the study, biasing the overall findings.  Finally, there would be no undue stress or harm in this study.  If anything, sharing the findings with the participants may actually help to prevent harm in the future.

There are several ways in which the researchers could increase the credibility of their findings. First, they could use triangulation.  They have used data triangulation, collecting data from five different locations. If the research is credible, then the trends will be seen in most, if not all of the locations. In addition, they could use researcher triangulation where different researchers carry out the interviews and process the data.  Once again, this would increase credibility - although in the case of structured interviews, this may not be as important as in other interview styles.  Using more than one researcher to carry out the interviews lowers the potential for interview effects playing a role in the study - that is, the way in which the attractiveness, gender, way of asking questions, body language - or any other behaviour on the behalf of the interviewer may have affected the responses of those being interviewed. With regard to the analysis of the interviews, the researchers should all come to the same conclusion about the data; this avoids researcher bias.

A final form of triangulation would be method triangulation.  In this case, using focus groups or observations of the participants' behaviour would let the researchers know if they get the same results with different methods, increasing the "validity" of their findings - and eliminating the potential of the method used influencing the results.

Another way to establish credibility is to ask the participants for feedback on the findings - do they think that this really reflects their behaviour?  If they confirm the findings, then this increases credibility.

Having a representative sample also increases the credibility of the study.  As these people were all at a cancer screening clinic, it is clear that they are concerned about the risk of cancer.  This may mean that they are not representative of the average Swede.

If the research findings confirm grounded theory - that is, past theory and research studies, then this increases the level of credibility.

Finally, having the researcher practice reflexivity can also increase the credibility of the findings. This is when the researcher reflects on his or her potential biases in the study or how the way that the research was carried out may have influenced the findings of the study. Acknowledging these limitations is an important part of establishing credibility.