What is the term used for a process that tries to measure some characteristic of every unit in a population?

The term "Census" refers to the process of collecting data from every single unit within a population. In this context, a census aims to measure specific characteristics for all individuals or items in the defined group, ensuring comprehensive data collection and analysis. This method contrasts with others, like sampling, which involves selecting a subset of the population to infer characteristics of the entire population. While surveys may gather information from a portion or all members, they do not inherently mean every unit is accounted for unless they are specifically designed as a census. Experimentation, on the other hand, focuses primarily on investigating hypotheses under controlled conditions rather than measuring population characteristics broadly. Therefore, census is the accurate choice for describing the process that attempts to measure every unit in the population.