Short Answer 
Convenience sampling involves selecting readily accessible participants, potentially leading to bias, while voluntary sampling relies on individuals’ self-selection based on interest, resulting in a more engaged but possibly unrepresentative group. The key differences include accessibility for convenience sampling versus personal interest for voluntary sampling, as well as how participants are selected and the potential for bias in each method.
Understand Convenience Sampling
A convenience sample is created by selecting participants who are easily accessible to the researcher. This means researchers choose individuals who are present or willing to participate without a structured selection process. Examples include surveying people in a local park or reaching out to friends and family. Because of this method, the sample may not represent the broader population accurately.
Recognize Voluntary Sampling
A voluntary sample is formed when researchers invite participants to join the study based on their own interest. In this approach, individuals decide if they want to participate, which can lead to a more engaged sample. Typical scenarios involve posting a call for participants online or using social media, allowing those who are interested to opt-in voluntarily.
Compare and Contrast the Two Methods
While both sampling techniques aim to gather data, they have distinct differences:
- Access: Convenience sampling relies on accessibility, while voluntary sampling is based on personal interest.
- Participant Selection: In convenience sampling, the researcher selects participants; in voluntary sampling, participants select themselves.
- Potential Bias: Convenience samples may introduce bias due to lack of randomness, whereas voluntary samples can attract highly motivated individuals, which may not accurately represent the population.