6.3: Non-probability sampling

Convenience sampling and judgement sampling are two examples of nonprobability sampling that are available to researchers and which we will examine more closely. A nonprobability sample is one in which each potential member of the sample has an unknown likelihood of being selected in the sample. Research findings that are from a nonprobability sample cannot be applied beyond the sample.

Convenience sample

The first nonprobability sampling technique is a convenience sample. Just like it sounds, a convenience sample is when the researcher finds a group through a nonscientific method by picking potential research participants in a convenient manner. An example might be to ask other students in a class you are taking to complete a survey that you are doing for a class assignment or passing out surveys at a basketball game or theatre performance.

One challenge with a convenience sample is selection bias, as the participants are chosen due to their easy access and not representative of the population. Since convenience samples might not reflect the population’s true diversity, findings from such samples might not be applicable or generalizable to broader populations or contexts. Another challenge with convenience samples are the risk of self-selection of participants. For example, potential survey respondents on a running trail may be selected since the researcher is at the edge of a park and is looking to get more information on park use, but this might not include folks who have mobility challenges, or parents pushing strollers who aren’t able to access the trail.

Market Research in Action: Daniel

 

Daniel works for Smoothtech, a mid-size technology company in the Greater Toronto Area who make specialized software and consumer apps for the sports and entertainment industries. Daniel is interested in learning more about how customers at the local theatre company obtain information from the playbill and if there would be interest in moving to a digital format.

Daniel thought that he could go to two Saturday matinees and stand inside the lobby to pass out surveys by the men’s washroom. This would be an easy place to find customers as they would be at the theatre already.

What are the challenges with Daniel using a convenience sample, particularly on a Saturday afternoon and by the men’s washroom. What biases may occur with this sample?

Judgement sample

A judgement sample is a type of nonprobability sample that allows the researcher to determine if they believe the individual meets the criteria set for the sample frame to complete the research. A judgement sample involves the selection of participants based on the researcher’s judgement about who would be most informative or representative of the population. For instance, one may be interested in researching mothers, so the researcher would outside a toy store and ask an individual who is carrying a baby to participate. The biggest challenge with a judgement sample is the potential for bias, as the researcher’s judgement might unintentionally favour certain individuals or groups, leading to a skewed representation of the overall population.

Market Research in Action: Daniel

Daniel wants to ensure that he has representative feedback from all parties who might be impacted by the decision of the theatre company to move to a digital playbill, so he considers using a judgement sample. This step will allow Daniel to assess if each respondent would meet the criteria to participate in the research.

Daniel could approach a judgement sample in this way:

1. Identify Key Partners: Determine the individuals or groups directly involved with or impacted by playbills in the theatre company. This might include regular theatergoers, actors, directors, production crew, and marketing / communications staff.
2. Select Diverse Perspectives: Ensure diversity in the sample by selecting participants from different demographics, such as age groups, socio-economic backgrounds, or levels of engagement with the theatre company.
3. Online Surveys: Send out an online survey to the email newsletter list. This can help gather a wider range of opinions and preferences regarding playbills and digital formats.
4. Engage Theatre Subscribers: Reach out to subscribers who purchase season passes to the theatre productions. These individuals might have strong opinions and insights into playbill usage as consistent patrons.
5. Utilize Social Media or Online Platforms: Gather opinions from online theatre communities, forums, or social media groups whereperforming arts enthusiasts discuss preferences and experiences related to playbills and digital mediums.

What are some of the challenges with gathering judgement sample, particularly one of those who are deeply involved in the theatre such as key partners, versus Facebook followers? What would be the benefits to a judgement sample?

Voluntary sample

In a voluntary sample, people “self-select” to participate in the survey. They may be interested in or feel strongly about the topic or they may want the perks or prizes for participating. There may be many motivations for them choosing to participate. The challenges with voluntary bias include self-selection bias, in that the volunteer is really excited for the prize and are not interested in providing a truthful response to the research. Another challenge with a voluntary sample is ensuring representation, as certain groups or demographics might be overrepresented or underrepresented, leading to findings that are not reflective of the broader population.

Here is a video from Pew Research Center on the recent increase in use of online nonprobability surveys, and its advantages and disadvantages.

References

Albrecht, M. G., Green, M., & Hoffman, L. (2023). Principles of Marketing. OpenStax, Rice University. CC BY 4.0

OECD (2012), “Good Practices in Survey Design Step-by-Step“, in Measuring Regulatory Performance: A Practitioner’s Guide to Perception Surveys, OECD Publishing, Paris.

Scholes, S. (n.d.). Introduction to Sampling Methods. OER Commons. CC BY-NC-SA 4.0