The association is the country's largest and oldest organization for special reports, journal articles, task forces, and conference programs dealing with issues relating to cell-phone interviewing, changing response rates, attitudes, election polling, and non-probability sampling using the Internet.
The penalty is that, in general, they are more resource-consuming than non-probability sampling methods.
Other methods involve non-probability sampling: for example, stopping prospective participants in the street.
Clients of these institutions are selected with purposive non-probability sampling technique.
The sampling method for this study was non-probability sampling based on a voluntary sample from a targeted population group.
When selecting the interviewees, I relied on non-probability sampling methods, specifically purposive or judgment sampling and snowball sampling.
Hence, if non-probability sampling is the only available option, serious consideration should be given to whether the study is worthwhile.
In both cases the field sample sizes typically are small or acquired through non-probability sampling whereas remotely sensed data are available wall-to-wall.
This leads the final survey to concentrate on an alternative means of data collection i.e. snowball sampling, a non-probability sampling method to identify the respondents.
The main shortcoming of this study is that its conclusions cannot be generalized, as it adopted a non-probability sampling method.
In non-probability sampling, selection bias is always there; the degree to which the sample differs from the population of interest is uncontrolled and may be large.
