Abdul Momin Kazi  ( Department of Pediatrics and Child Health, Aga Khan University, Karachi, Pakistan. )
Wardah Khalid  ( Department of Pediatrics and Child Health, Aga Khan University, Karachi, Pakistan. )

Introduction and Objectives:
Measurement is an essential activity of medical science. In order to acquire data about people, objects, and events proper data collection tools need to be designed which can measure things of scientific interest. Questionnaire is one of the most important techniques to collect data. It is a common experience that many studies focus on similar objective and theme but have entirely different questionnaires. It is extremely important for a researcher to know the importance of a proper questionnaire and whether it measures what it is intended to measure. Composing of a questionnaire is always much more complex than expected and great attention is required to its flow, format and length. Making an individual question is a tedious task and validating this questionnaire is another challenge which at times is over looked. Consideration should be given accordingly on whether the questionnaire will measure quantitative or qualitative data, and what would be its mode of administration.
The aim of this paper is to give a basic introduction and broad overview to the readers on questionnaires for epidemiological studies.
Questionnaire Development:
A questionnaire is a tool to obtain information from respondents. 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. These questionnaires do not need to be tested for reliability and results can be compared for different studies and also combined for meta- analysis. However one needs to make sure that the mode of administration should be similar to the original questionnaire.¹
If a new questionnaire is to be developed, it should be pilot tested and validated in order to evaluate if it is measuring what it supposed to measure and is it doing it reliably. Wording of questions is very critical and should take into consideration; appropriateness of the content, level of sophistication of language, type and form, sequence and how is data sought from the respondents. During questionnaire development its mode of administration should be kept in mind, whether it will be self-administered or interview based and its design and flow should be planned accordingly.²


See Table on common problems in questionnaire.
The language of questionnaires should be at the level of understanding of the participants. It is essential to word the questions in a way that they can easily be understood by participant and should be according to their educational level and culture. 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.³
Translation of a questionnaire is essential if an instrument is not available in a language understood by the target population. The initial stage of translation is a source language questionnaire, from which translation in required language is done. 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. Translation should not only be concerned with translating meanings, but it should also understand how the language is tied to local realities and literary forms. The term back translation is highly recommended in questionnaires related to health surveys. Back translation helps in evaluating the quality of the translation. The source language is translated in another language and again translated back into the source language. Translation back to the source language is done by another translator who is unaware of the source language version.⁴
Validity:
Validity is the degree to which an assessment measures what it is supposed to measure. Validity is a complex topic and it is beyond the scope of this paper to explain it in detail, however to make the readers acquainted we have described it briefly. Essentially there are three types of validity i) content validity, ii) criterion- related validity, and iii) construct validity.⁵ 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. A valid questionnaires must have following characteristics (i) simplicity and viability (ii) reliability and precision in the words (iii) adequate for the problem intended to measure (iv) reflect underlying theory or concept to be measured and (v) capable of measuring change.⁶
Type of Questions:
A questionnaire is a written document to gather information irrespective of mode of administration. A questionnaire could be structured, in which all the participants are asked same questions in the same way, this is usually interview based questionnaire format. The other type is unstructured questionnaire and questions may vary at the discretion of the interviewer. Unstructured format may be used at clinical setting however structured questionnaire is preferred for epidemiological studies as same data from all respondents need to be analyzed and measured.⁷
Open-ended questions allow respondents to answer them in any way they want. For continuous variable this format is more suitable when large numbers of options are available and it is not practical to write all answers in advance e.g. weight of the patient. All possible answers are not written in advance and needs to be coded latter and may increase chance of error. The open ended questions might increase the burden on work and responses have to individually review by the investigator before assigning codes and analyses.
Closed-ended questions in contrast would ask the respondents to make choices among a set of answers in a given question. The response could be mutually exclusive or may select more than one option. For measuring dichotomous variables closed- ended questions are preferred because possible answers can be easily precoded. Precoded questions are defined as those in which numbers are assigned to a given answer. Precoding saves time for assigning number latter and hence decrease error; however for open-ended questions coding is done after the data is collected. Coding helps in data entry, as information of questionnaires in paper format are entered in data entry programs by putting in the numbers rather than writing the whole answer.
Questionnaire Style and Appearance:
The appearance and style of the questionnaire is very important and has a very strong impact especially in self-administered questionnaire. Format, order, spacing, fonts used and grouping of the response are very important features in overall layout of the questionnaire and have a direct effect on the responses and time spent by the respondent to provide it. Questions should be simple, clear and easy to understand, using minimum of words and space and only asks what needs to be asked. Lengthy or confusing lay out of the questionnaire can also make the interviewer confused and responses administered by the interviewers may not be accurate or complete. The clarity of questionnaire has direct impact on data collected by the interviewer and responses given by the responders.
Mode of Administration:
Broadly speaking there are two modes of administrating a questionnaire, a) self-administered and b) interviewer administered questionnaire.
Self-administered questionnaire only requires questionnaire distribution; it is much cheaper and doesn\\\'t need trained staff. This mode is less susceptible to information bias and interviewer effect but have greater chance of having no response items. The main advantages of self-administered questionnaires is that it can reach a large sample size, cover wide geographical area, cover population which is sometimes difficult to reach, excellent for capturing sensitive topics and cheaper as compared to other modes of administration.
Common method of self-administered questionnaire distribution is either through mail or electronic distribution. Participants can complete mailed questionnaire at their convenience, in their homes and at their own pace. Major disadvantage of the mailed questionnaire is low response rate even after repeated mails, and queries of the participant cannot be clarified. Some effective techniques for improving the rate of response are; sending follow-up letters, enclosing some incentives, providing self-addressed stamped envelope and keeping the questionnaire brief.
Electronic and web-based questionnaire, including data collected through personal digital apparatus (PDAs), smart phones and cell phones are latest techniques for questionnaire administration. Questionnaire can be designed to filter and screen participant\\\'s response, checks for input error, range and skip patterns can be incorporated preventing significant typing and data format error.⁸ However electronic questionnaire is restricted to those participants who have access to a computer and internet and this can be a potential bias.
In person or interview based administration is expensive but provides direct interaction with the participant. The interviewer has the opportunity to introduce the research topic and motivate the participant to offer their frank answers and questions can be clarified at the spot. If the interviewer is trained and motivated, it is the best method to collect data in epidemiological studies. In recent era telephone use has also increased for administrating questionnaire. This is cost effective and usually have greater response rate as compared to postal questionnaire. Telephone interviewing also facilitates in covering a large number of participants over a wide geographical area.⁹ Interviewer on the phone can directly talk to the participant, explain the study and clear any confusion or questions during the call. Possible disadvantage of phone call is that the caller cannot see the participant and might have difficulty in rapport, cannot use additional material for explaining the questionnaire. For example pictures and study involving sample collection cannot be conducted through phone administered questionnaires.

A questionnaire designed for epidemiological studies should capture information from participants regarding their exposure, possible risk factors, and occurrence of disease of interest. This paper tried to help researcher in designing questionnaire and broadly explained the different method of questionnaire development, validity, types of questionnaire, their style and appearance and mode of administration.

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