Translation back to the source language is done by another translator who is unaware of the source language version.Validity: Validity is the degree to which an assessment measures what it is supposed to measure.
Translation is not a mechanical work and should not be done on word to word bases across languages.
It is important to understand the local context, specific issues and cultural meanings which language carries.
If the questions are interpreted differently by the participants it will result in wrong answers and responses will thus be biased.
Reading ease of a questionnaire can be assessed by Flesch reading ease score.
It is an efficient way to collect data, the investigator should be certain on what is required and how to measure the variables of interest.
As a first step it is always recommended to do a literature search on previously used validated questionnaires that can be administered in similar settings and capture variables that are of interest according to the study hypothesis.
A questionnaire undergoes a validation procedure to make sure that it accurately measures what it aims to do, regardless of the responder.
Valid questionnaire helps to collect better quality data with high comparability which reduces the effort and increase the credibility of data.
The aim of this paper is to give a basic introduction and broad overview to the readers on questionnaires for epidemiological studies.