Web-based experiments and questionnaires are essential epidemiologic tools that provide important information about public health and disease. They are the most commonly used methods of collecting data that are often more affordable and efficient than face-toface interviews, mail-in questionnaires, or automated telephone menu systems. However questionnaires, surveys and Web experiments have significant limitations that must be addressed in order to ensure the validity and reliability of results.

A questionnaire can be affected by response bias. This is the tendency for respondents to answer questions based on their opinions instead of research goals. In addition, the design of the questionnaire can influence responses in a variety of ways. For example the language used in the questions can affect whether respondents comprehend and interpret the questions in the same way (reliable) to determine the topic you’re interested in (valid), or are able to answer the question accurately (credible).

Respondents might also experience survey fatigue or a lack of interest in the questions being asked and reduces the chance of them providing honest responses. Lack of incentives or compensation can also discourage participants from filling out survey forms.

Online questionnaires can also be an issue for certain experimental designs, like studies of response time or positioning. It is difficult to measure and control variables across participants because of the different settings for browsers as well as operating systems and the size of screens.

Finally, Web-based surveys are only accessible to people who have keyboards and are Internet literate, which currently excludes a significant portion of the population. Additionally, it is usually difficult to Web researchers to debrief participants when the window for an experiment has closed.

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