| Summary: | This article examines practical epidemiology principles related to the design and implementation of web surveys. Six practice-oriented items are critically examined: 1) The study question; 2) The target population; 3) Study population needed; 4) Sampling or selecting the
participants in a representative manner; 5) Sending the
survey invitations in a manner that is efficient, safe, and
mitigates bias; and 6) Assessing and enhancing the external
validity of collected data. Clearly articulating the study’s
purpose (including whether there is an intent to create
generalizable knowledge) influences the sampling approach:
probabilistic or non-probabilistic. Similarly, properly
defining the study population (people, place and time)
prevents overgeneralization of study findings. Adjustments
to sample size may be needed to address different real-world
complexities, including multi-purpose surveys with different
(possibly un-related outcomes), multiple target populations,
subgroup analyses, and cluster sampling. When the sample
is being drawn from a sampling frame, efforts must be made
to ensure that the frame is complete, current, and correct to
reduce under-sampling. The choice of environment in which
data collection is hosted is critical; practical considerations
include data volume, variety, vulnerability, and the software’s
capabilities and cost. Although web surveys, in general, are
becoming increasingly easier to conduct, good web surveys
in contrast are becoming increasingly harder to undertake.
Careful consideration should be given to sampling and non-sampling
sources of error when designing web surveys to
ensure validity and reliability.
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