How should I describe the population and sampling unit before planning a study?

Define the target population, sampling unit, and measured unit separately.

The target population is the group you want the study to describe. The sampling unit is what you select when drawing or inviting your sample. The measured unit is what you record information about. A sample is a subset of a population, and a study can name its target population, participating sample, and individual units separately. [S1][S2]

For a hypothetical workshop survey, you might intend to describe adults who attended a particular set of community workshops during a stated period. You might select individual attendees from a list, then record each attendee’s answers. In that plan, the individual attendee is both the sampling unit and measured unit. Treat those as assumptions to check against your actual study, not as facts about your workshops.

Usually, that wording leaves key boundaries unstated. Decide which people your question is about, and specify the relevant workshop group and time period. For example, “people who attend workshops” could mean anyone who has ever attended any workshop, while your actual plan might concern attendees of a defined series during a particular season.

A useful test is to ask whether another person could decide, using your description, whether a particular person belongs in the target population. If not, add the missing boundary. Do not silently narrow the population to whoever is easiest to contact: if your intended group is broader than the people you select or reach, say so. The source definitions distinguish the target population from the participating sample; they do not choose the right population for your specific question. [S1]

Yes, as a planning description, you can distinguish selecting workshops from measuring answers from individual attendees. State both steps explicitly: “We select [workshops] and record responses from [individual attendees].” In that setup, a workshop is the unit selected at the first step, while an attendee is the unit whose information you record. If you also select particular attendees within each chosen workshop, name that additional selection step rather than calling the whole process simply “a sample of attendees.”

Alternatively, if you select people directly, write that the sampling unit is an individual attendee. The important point is not to imply that workshops themselves supplied individual responses. OpenStax’s example supports identifying the target population, participating sample, and individual units separately, but it does not prescribe a sampling design for community workshops. [S1][S2]

Use this template before settling the survey plan:

“Target population: [the group the study aims to describe], defined by [relevant membership, setting, and time period]. Sampling unit(s): [what will be selected, and at which step]. Measured unit: [the person or object for which information is recorded]. Sample actually reached: [who or what participated, once known]. Measure: [the characteristic or answer recorded for each measured unit].”

Worked hypothetical example: “Target population: adults who attended [named workshop series] during [defined period]. Sampling unit: individual attendees selected from [the planned list or contact method]. Measured unit: each individual attendee who answers. Sample actually reached: [to be filled in after collection]. Measure: each respondent’s answer to [survey question].” This assumes a list and direct attendee selection; if your plan selects workshops first, replace the sampling-unit line with that step and explain how attendee respondents are chosen.

Keep “sample actually reached” as a placeholder until you know who participates. A plan alone does not establish who will respond or whether the resulting sample represents the target population.