The population information is called parameter while the corresponding sample…

Concept — In statistics a numerical summary is named after the group it is computed from. A numerical characteristic worked out from every unit of the whole population — its mean, proportion or variance — is called a parameter, and it is a fixed constant that is usually unknown. The corresponding numerical characteristic worked out from only the units that fall in a sample changes its name accordingly, and its value changes from one sample to the next.

Application — The stem fixes the pairing “population information → parameter” and asks for the counterpart on the sample side of that same pairing. The only thing that changes across the pair is the group the number is computed from — the whole population versus the drawn sample — so the sample-side name is statistics. In the wording of this paper that name appears as “Statistics”, and the singular form used for one such measure is “a statistic”. It is the quantity a researcher can actually calculate from collected data, and it is then used as an estimator of the unknown parameter.

Cross-check — read each offered term against this population-versus-sample axis:

• Universe — a synonym for the population itself, the complete collection of units under study, not a number computed from them.

• Inference — the reasoning that generalises from sample evidence to the population through estimation and tests of hypotheses, carried out after the sample number exists.

• Sampling design — the plan that fixes how units are selected (frame, technique, sample size), settled before any observation is measured.

• Statistics — the numerical measures computed from the sample observations, which are precisely the sample-side counterpart of a population parameter; one such measure is called a statistic.

Hence the sample counterpart of a population parameter is statistics.