Factors affecting the reliability of a research instrument

In the social sciences it is impossible to have a research tool which is 100 per cent accurate, not only because a research instrument cannot be so, but also because it is impossible to control the factors affecting reliability. Some of these factors are:

• The wording of questions – A slight ambiguity in the wording of questions or statements can affect the reliability of a research instrument as respondents may interpret the questions differently at different times, resulting in different responses.
• The physical setting – In the case of an instrument being used in an interview, any change in the physical setting at the time of the repeat interview may affect the responses given by a respondent, which may affect reliability.
• The respondent’s mood – A change in a respondent’s mood when responding to questions or writing answers in a questionnaire can change and may affect the reliability of that instrument.
• The interviewer’s mood – As the mood of a respondent could change from one interview to another so could the mood, motivation and interaction of the interviewer, which could affect the responses given by respondents thereby affecting the reliability of the research instrument.
• The nature of interaction – In an interview situation, the interaction between the interviewer and the interviewee can affect responses significantly. During the repeat interview the responses given may be different due to a change in interaction, which could affect reliability.
• The regression effect of an instrument – When a research instrument is used to measure attitudes towards an issue, some respondents, after having expressed their opinion, may feel that they have been either too negative or too positive towards the issue. The second time they may express their opinion differently, thereby affecting reliability.

Source: Kumar Ranjit (2012), Research methodology: a step-by-step guide for beginners, SAGE Publications Ltd; Third edition.