Online Medical Info. USA Today posted this question on its website: “How often do you seek medical information online?” Of 1072 Internet users who chose to respond, 38% of them responded with “frequently.” What term is used to describe this type of survey in which the people surveyed consist of those who decided to respond? What is wrong with this type of sampling method?

The sample consists of 1072 internet users who responded at their own will.

Out of these, 38% responded “frequently” for the website question “How often do you seek medical information online?”

In this survey, the sample responses were collected from individuals who chose to respond to the survey. The type of sampling is called voluntary response sampling, in which the sample points are self-selected.

Thus, the term that could be used for such survey designs is voluntary sampling.

When a study is designed on voluntary sampling responses, the responses are not free of bias.

In this case, the sampled individuals themselves opted for the study and hence cannot be considered as true representatives of the population of all internet users.

A true representative would have responses that would be randomly selected from the population.