Who Gets Counted?

Sampling, survey data, and the conclusions we draw from them

Learning Outcome

Evaluate whether conclusions drawn from survey data are supported by the population sampled and the method used to collect the data.

Sampling and Survey Data

Researchers, businesses, government agencies, healthcare organizations, and other institutions frequently use surveys to learn about people, behaviors, attitudes, preferences, and experiences. Because it is often impractical to collect information from every person in a population, researchers collect information from a sample.

The quality of conclusions drawn from survey data depends partly on who is included in the sample and how participants were selected. A large sample does not necessarily represent the larger population if some groups are more likely than others to be included or respond.

Common sampling approaches include random sampling, convenience sampling, voluntary-response sampling, and other methods. Researchers should consider whether a sample is representative of the population they want to understand and whether the sampling method may introduce bias.

Key Terms

Key terms used when evaluating survey samples
Term	Definition
Population	The full group a researcher wants to understand.
Sample	The smaller group from whom data are actually collected.
Representative sample	A sample that reasonably reflects characteristics of the population being studied.
Voluntary-response sample	A sample made up of people who choose to participate.
Sampling bias	A systematic problem that makes some members of the population more or less likely to be represented.
Generalizability	The extent to which conclusions from the sample can reasonably be applied to the larger population.

Required Resources

Read the assigned textbook section on sampling methods.
Review the lecture slides on populations and samples.
Review the examples of random, convenience, and voluntary-response samples.
Watch the assigned video on sampling bias.

Watch: Sampling and Bias

Sampling and Survey Bias
[VIDEO PLACEHOLDER]

Video Transcript

[TRANSCRIPT PLACEHOLDER]

City Transit Survey

A city wants to understand how residents use public transportation and what would make them more likely to use it.

The city posts a survey link on the public transit agency's website and shares it through the agency's social media accounts. The survey remains open for four weeks.

A total of 2,846 people complete the survey.

82% of respondents report using public transportation at least once per week.

Based on the survey results, the city reports:

Most city residents regularly use public transportation.

Assignment

Analyze the survey and determine whether the city's conclusion is supported by the data.

In your response, discuss the sample, the sampling method, possible bias, and whether the results can be generalized to the city's population.

Submit a 400–600 word analysis.

Points: 50