Population Sampling Methods
The word population has a very specific meaning in statistics. The population is the total collection of objects to be studied, from which a sample is to be draen. The objects may be people, buildings, plants, salaries, factories etc. In other words, all distinct species (familes of all objects) lies on this universe are called population of specific species.
For example, planets are species and in the sciences and in the science of statistics, it is a population. Furthermore, the streams, workers working in a factory or factories is also a population. The population can be any size. It might be only 200 students in a certain class or 10,000 people in a city.
The concept of population is most fundamental idea in statistics. The population of concern must be carefully defined and is considered fully defined only when its membership list of elements is specified. The set of "all students who have ever attended xyz college" is an example of a well-defined population. There are two kinds of populations, finite and infinite
The population is said to be finite, when the membership of population can be physically listed. (limited) e.g., The books in Ewing Memorial Library of FCC, all the registered voters in a country from a very large finite population. The number of boys enrolled in all colleges this year. The number of tress in a jungle etc.
The population is said to be infinite, when the membership is unlimited ( i.e., cannot be physically listed), e.g., the population of all people who might use asprin. The population of all 100-watt light bulbs to be produced by a company. The grains (particles) of sands in the desert. the stars in the sky. The number of fishes in a lake etc.
Large population are difficult to study; therefore, it is customary to select a sample and study the data in the sample. A sample consist of the individuals, objects, or measurements selected by the sample collector from the population e.g the cars owned by a perticular college students would be a sample. Usually we have detailed information about individuals in the sample, but not for those in the population (universe).
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