Collection of information from the representative units in the sample is known as:

Census is the collection of information from all individuals in a population. Sampling is the process or technique of selecting a sample of appropriate characteristics and adequate size. Advantages of sampling It reduces the cost of the investigation, the time required and the number of personnel involved. It allows a thorough investigation of the units of observation. A sample can be covered more adequately and in more depth than can a total population. Reference: Essentials of Preventive and Community Dentistry, Soben Peter, 4th ed page no 288