snowball sampling

Snowball SamplingSnowball sampling is an approach for locating information rich key informats. In this approach few potential respondents are contacted and asked whether they know anybody with the characteristics that you are looking for in your research.

For example, if you wanted to interview a sample of vegitrians, or cyclists or people with a particualar disability, etc your initial contacts may have a knowledge.

Snowball sampling is not a stand-alone tool; the tool is a way of selecting participants and then using other tools, such as interviews or surveys. Having identified those with the skills and/or knowledge or characteristics you require, you would then approach these people to invite them to participate in a community consultation process.

Objectives:

Snowball sampling is designed to identify people with particular knowledge, skills or characteristics that are needed as part of a committee and/or consultative process. Snowball sampling uses recommendations to find people with the specific range of skills that has been determined as being useful, as such, snowball sampling aims to make use of community knowledge about those who have skills or information in particular areas.

Outcomes:

Snowball sampling allows you to identify the resources within a community and to select those people best suited for the needs of a project or process.

Uses/strengths:

Helps to determine stakeholders. Increases the number of participants in process.
Builds on resources of existing networks. Determines stakeholders unknown to you.

Special considerations/weaknesses:

Choice of initial contacts is most important.
Participation process should be drafted prior to the sampling to encourage participation from potential contacts.

http://www.statpac.com/surveys/sampling.htm
http://ccnmtl.columbia.edu/projects/qmss/samp_type.html