Interviewer bias

Interviewer bias is a type of information bias that arises when an interviewer consciously or unconsciously elicits inaccurate information from study subjects. Interviewer bias can result in differential error, which can seriously distort disease - exposure associations, if the interviewer is aware of the exposure status and outcome hypothesis in a cohort study.

In the former case, the interviewer may probe more deeply for evidence of exposure among cases than among controls. In latter case, the interviewer may try to elicit evidence of health effects more assiduously in exposed than in unexposed cohort members. Methods used to minimize interviewers to follow a fixed pattern of questioning, and, where possible, keeping interviewers unaware of the disease status and exposure hypotheses of greatest interest in case - control studies, and unaware of exposure status and health outcome hypotheses of greatest interest in cohort studies.

Possibility of interviewer bias should be taken seriously in all research. Although it may not be possible to eliminate all forms of interviewer bias, there are a number of measures that can be taken to avoid and control potential biases.

Ways in which bias occurs

Number of ways in which bias occurs, namely:

• departures from the interviewing instructions
• poor maintenance of rapport with the respondent
• altering factual questions
• rephrasing of attitude questions
• careless promoting
• biased probes
• asking questions out of sequence
• biased recording of verbatim answers

One way of avoiding, or at least minimizing, interviewer bias is to require all interviewers to follow the same protocol. Hence, a set of guidelines might be drawn up which ask the interviewer to read the questions exactly as they are written, to repeat a question if asked, to accept respondent's refusal to answer a question without any sign of irritation, and to probe in a non-directive manner.

Types of interviewer bias

There are several types of interviewer bias:

• Personal interview. Facial expressions and tone of voice could affect responses. However, monitoring interview sessions (e.g., videotaping them or watching them through a one-way mirror) could prevent and detect interviewer bias.
• Phone interview. Tone of voice could affect responses. However, having a supervisor monitor interview sessions or taping sessions could prevent and detect interviewer bias
• Investigator administered Minimal interaction with investigator, so little chance of interviewer bias
• E-mail surveys, web surveys. No interviewer, no interviewer bias.

Examples of Interviewer bias

1. Leading Questions: Leading questions are questions that suggest or hint at the ‘correct’ answer. They can be used to guide an interviewee towards a response that the interviewer may favor.
2. Assumptions: Assumptions are beliefs that the interviewer holds which may affect the way they interpret answers. This can lead to a biased interpretation of the responses.
3. Filtering: Filtering involves omitting certain questions or responses that do not fit with the interviewer’s beliefs or expectations.
4. Unclear Questions: Unclear questions can lead to a lack of clarity in the responses. This can lead to misinterpretation and bias.
5. Non-Verbal Cues: Non-verbal cues such as body language and facial expressions can give the impression that the interviewer is favoring one response over another. This can lead to biased answers from the interviewee.

Advantages of Interviewer bias

Interviewer bias can provide valuable insights into a person’s feelings and attitudes, as the interviewer has the opportunity to ask follow-up questions and probe for more detailed answers. This can result in a more in depth understanding of the subject's views and motivations. Additionally, interviewer bias can provide an opportunity for the researcher to build rapport with the respondent, as the researcher can adjust their approach to the respondent’s personality and better connect with them. Moreover, face-to-face interviews can also create a greater sense of trust and understanding between the researcher and the respondent, as the researcher can address any concerns the respondent may have. Finally, interviewer bias can be helpful in identifying and addressing potential issues with the data, as the researcher can assess the respondent’s level of understanding and ability to answer the questions. *

Limitations of Interviewer bias

Interviewer bias can lead to several limitations in research:

• It can lead to inaccurate data due to interviewer's own biases and preconceived notions.
• It can lead to selective recording of information, which can cause data to be incomplete or incorrect.
• It can lead to inaccurate responses from study participants as they may not feel comfortable revealing their true opinions or feelings to the interviewer.
• It can lead to low response rates if participants feel intimidated or uncomfortable with the interviewer.
• It can lead to inaccurate interpretations of data due to interviewer's own beliefs or assumptions.
• It can lead to a lack of diversity in the sample if the interviewer is biased towards a certain demographic.

Other approaches related to Interviewer bias

Following are some of the approaches to reduce interviewer bias:

• Interviewer training: This involves training interviewers to minimize the potential for bias and develop an understanding of the research objectives. It includes providing them with an understanding of the research objectives and a clear set of instructions for carrying out the interview.
• Standardization of interview methods: This involves ensuring that the same questions and instructions are used for each interview. This helps to ensure consistent data collection.
• Blinded interviews: This involves the interviewer not knowing the participant's identity or other personal information. This helps to ensure that the interviewer remains impartial and not influenced by any preconceived notions.
• Double interviewing: This involves using two interviewers to interview the same participant. This helps to ensure accuracy and consistency in data collection.

In summary, the approaches to reduce interviewer bias include interviewer training, standardization of interview methods, blinded interviews, and double interviewing. These approaches help to ensure accuracy and consistency in data collection, and reduce the potential for bias in the results.

Footnotes

Interviewer bias — recommended articles

Lurking variable — Leniency error — Social desirability bias — Group conformity — Testimonial evidence — Experimental error — Disciplinary procedure — Common method bias — Types of validation

References

• Gail M.H., Benichou J., (2010), Encyclopedia of Epidemiologic Methods, John Wiley & Sons, New York.
• Gray D.E., (2010), Doing Research in the Real World, SAGE, London.
• Mitchell M.L., Jolley J.M., (2010), Research Design Explained, Cengage Learning, Australia.
• Reis H.T., Judd C.M., (2000), Research Methods in Social and Personality Psychology, Cambridge University Press, Madrid.

Author: Natalia Węgrzyn