A college principal conducts an ethnographic probe into the problems faced by…

Concept: In probability sampling, the population can be divided in different ways before units are drawn. Stratified sampling divides the population into distinct strata based on a defining characteristic and draws units from every stratum, mainly so that different strata can be compared. Random and systematic sampling both draw scattered individual units, by chance or at a fixed interval, without regard to any group structure. Cluster sampling, by contrast, samples by selecting whole naturally occurring or administratively defined groups (clusters) — such as villages, hostels, or wards — rather than by drawing scattered individuals or by partitioning the population into contrasting strata.

Application: Tribal students in a college are typically concentrated within specific natural or administrative groupings, such as particular hostels, intake batches, or home villages/wards, rather than spread evenly and individually across the institution. To reach this population for an ethnographic probe, the most practical approach among the four offered methods is to identify such groupings and select some of them wholly for study, which is exactly the logic of cluster sampling. This is why cluster sampling is the exam's keyed choice among the offered alternatives, even though, strictly speaking, sampling a sub-population defined by one characteristic (tribal status) is closer to a targeted or purposive selection: formal cluster sampling selects intact natural or administrative clusters, which may themselves be internally mixed, not a subgroup defined directly by that one characteristic.

Cross-check: Checking against the other three options confirms the fit. Random sampling would draw scattered individuals from across the whole student body without regard to where tribal students are concentrated. Stratified sampling would require dividing the entire student population into multiple strata (for instance, tribal versus non-tribal) and sampling from every stratum for comparison, which serves a comparative purpose rather than a focused study of the groups where tribal students are concentrated. Systematic sampling applies a mechanical fixed-interval rule to an ordered list, which again does not target any specific natural or administrative grouping. (In practice, ethnographic fieldwork on a single named community is often carried out through purposive selection of that community rather than by formal probability sampling; among only the four probability-sampling methods offered here, however, cluster sampling — reaching the tribal-student population through the natural or administrative clusters it is concentrated in — is the standard, exam-keyed answer.)

Cluster sampling is therefore the most appropriate method among those offered for this ethnographic probe.