Population and Sample
The main objective of studying statistics is to characterize population, defined as the collection of well-defined entities having some common characteristics. The observations or entities could refer to anything like persons, plants, animals, and objects (books, pens, pencils, medicines, engines, etc.), and a character is defined on the population. Population may be constituted of persons living in a country, population of goats in a country, population of books in a library, population of fishes in a particular pond, population of farmers in a country, populations of students in a country/state/university, etc. Individual member of the population is known as element or unit of the population. Population size refers to the number of observations in the population. Depending upon the size of the population, a population may be finite or infinite. A finite population is having fixed number of observations/units/elements, e.g., population of students in a university, germplasms of mango in a mango garden, books in a particular library, population of cattle in a province, and so on. On the other hand, an infinite population is having infinite number of observations/units/elements. For example, fishes in a particular river, stars in a galaxy, population of hairs on a person’s head, etc. An infinite population may be infinite or countably infinite.