Reliability of questionnaires used in health sciences

The interview is one of the most frequently used strategies in health research. Tools which help to obtain accurate data are essential. This is why questionnaires are used. However, a questionnaire is considered useful only if it has certain characteristics such as validity and reliability. Internal consistency, test-retest and inter-observer reliability are evidence that a questionnaire is reliable. All of the above must be demonstrated in order to ensure reproducible results. These properties should be tested in each study sample, to ensure the reproducibility of the results and support the existing evidence that the tool is a good measurement or not.