Editing Sampling (statistics) (section)

===Voluntary sampling===
{{further|Self-selection bias}}

The voluntary sampling method is a type of non-probability sampling. Volunteers choose to complete a survey.

Volunteers may be invited through advertisements in social media.<ref name=":1">{{Cite web|url = https://heal-info.blogspot.com/2017/07/voluntary-sampling-method.html|title = Voluntary Sampling Method combined with Social Media advertising|access-date = 18 December 2018 |website = heal-info.blogspot.com |series= Health Informatics |last = Ariyaratne | first = Buddhika | date= 30 July 2017}}{{unreliable source?|date=December 2018}}</ref> The target population for advertisements can be selected by characteristics like location, age, sex, income, occupation, education, or interests using tools provided by the social medium. The advertisement may include a message about the research and link to a survey. After following the link and completing the survey, the volunteer submits the data to be included in the sample population. This method can reach a global population but is limited by the campaign budget. Volunteers outside the invited population may also be included in the sample.

It is difficult to make generalizations from this sample because it may not represent the total population. Often, volunteers have a strong interest in the main topic of the survey.