Last Updated on October 3, 2026 by Karl Thompson
Reliability means that a research method gives consistent results. If the same research were repeated, by the same researcher or a different one, a reliable method would produce the same findings. Another way to put this is that reliable research can be replicated.
Reliability is part of research design in Theory and Methods, which is assessed on Paper 1 and Paper 3 (mostly Paper 3). It is one of the main evaluation points you can make about any research method, so you will need it in methods in context questions on Paper 1 as well.
What is reliability in sociology?
In sociology, a method is reliable if different researchers using it in the same way, or the same researcher using it at different times, get the same results. A bathroom scale that always tells you that you weigh three kilograms less than you really do is reliable, because it gives the same reading every time, but it is not valid, because the reading is wrong. Reliability is about consistency, and validity is about whether the results are true.
Reliability matters because it allows other researchers to check findings by repeating the research. If a different researcher cannot get the same results using the same method, the original findings are open to doubt.
Reliability and the positivist and interpretivist debate
Reliability is one of the main points of disagreement between Positivists and Interpretivists.
Positivists put reliability first. They want sociology to work like a science, with findings that can be checked and compared, so they favour methods which follow a fixed, standardised procedure: the same questions in the same order, asked in the same way to every respondent. Anyone can then repeat the research.
Interpretivists accept that their methods are less reliable and argue that this is the price of getting a valid picture. Unstructured interviews and participant observation depend on the relationship between the researcher and the people studied, and on the researcher’s own judgement about what to ask, notice and record. No two researchers would do it in exactly the same way, and the situation itself can never be recreated, so another researcher cannot repeat the study and check it.
| Method | Reliability |
|---|---|
| Questionnaires and structured interviews | High. The same standardised questions are put to every respondent, so the research is easy to repeat |
| Laboratory experiments | High. The procedure and the conditions are controlled, so the experiment can be repeated |
| Unstructured interviews | Low. Each interview is different, and the results depend on the interviewer’s skills and the rapport they build |
| Participant observation | Low. A unique situation which cannot be repeated, and the findings depend on what one researcher noticed and chose to record |
HOWEVER, a reliable method is not automatically a good one. A questionnaire can be repeated and give the same results every time and still fail to show what people really think, which is why Interpretivists argue that validity matters more.
Reliability and validity
The two ideas are linked, and the link is worth using in evaluation. A measure that is not reliable cannot be valid, because if it gives different results each time it cannot be giving a true picture. But a reliable measure may still be invalid, because it can be consistently wrong. In practice there is often a trade-off: the standardised methods that are most reliable tend to be the ones Interpretivists see as least valid, and the methods they see as most valid tend to be the least reliable.
Three ways to assess reliability
Reliability refers to the consistency of a measure of a concept. There are three factors researchers generally use to assess whether a measure is reliable:
Stability (test-retest reliability)
Is the measure stable over time, or do the results fluctuate? If we administer a measure to a group and then re-administer it and there is little variation in the results over time, the measure can be said to have ‘test-retest reliability’.
Internal reliability
Are the indicators which make up the scale or index of a measurement consistent? If the scores a respondent achieves according to one indicator of a measure are consistently related to the scores they achieve according to other indicators for that same measure, then the measure can be said to have ‘internal reliability’.
Inter-rater reliability
How much agreement is there over which observed empirical phenomena fit into what indicator? If researchers have a high level of agreement over how observed behaviour ‘map onto’ the indicators of a measure, then we can say the measure has a high level of inter-rater reliability.
These three types are extension material. You do not need all of them to write a good evaluation point about reliability, but they show you the technical side of the concept.
Using reliability in the exam
Don’t just write that a method is “reliable” or “not reliable”. Explain why it can or can’t be repeated. For example, with a structured interview you might say that the same questions are asked in the same order to every respondent, so another researcher could repeat the research and check the results. Then link the point to the research context in the question, and to whether the researcher is taking a Positivist or an Interpretivist approach.
Remember to keep reliability and validity separate. A common mistake is to use the two words as if they mean the same thing.
Source
Bryman, Alan (2016) Social Research Methods
Theory and Methods A Level Sociology Revision Bundle
If you like this sort of thing, then you might like my Theory and Methods revision notes bundle – specifically designed to get students through the theory and methods sections of A level sociology papers 1 and 3.
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Signposting
This post has been written primarily for students studying theory and methods, as part of the AQA’s A-Level Sociology course.
Reliability goes hand in hand with validity, and the two are usually evaluated together. The disagreement between Positivists and Interpretivists over which matters more is covered in Positivism and Interpretivism in Sociology. For how researchers choose who to study, see sampling, and for the whole topic see the research methods hub.
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