When researchers conduct a survey questioning all members of a population, they are employing a . However, if the researchers question a subgroup of the population, they are employing a .

census; sample

Explanation:

In order to conduct surveys there is need to have a population in which samples can be collected whether randomly, systematically or in a cluster manner.

When there is a need to conduct a survey questioning all members of a population it means one wants to involve in a survey.

In the human world, the government may wants to know how many people falls into a particular gender, race, age group and so on. When the government (researchers) do this it means that they wants to perform or they are performing what is known as CENSUS.

When a small group is subjected to research out of the general group then we say that SAMPLE is been drawn out.

Important: Note that the term ''population'' does not refer to human being alone it can be members of another 'thing' for instance animals like birds, goats and so on.

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