Population
and sample
In this
section we discuss about concept of population and sample in statistics.
Concept of Population in
Statistics
In any statistical investigation, we are
interested in studying the various characteristics of individuals (or items) of
a particular group. This group of individuals under study is known as the
population or universe. For example, if we wants to study the expenditure
habits of the families in that city, then the population will consist of all
the households in that city.
Thus in statistics, population is the aggregate
of objects, animate, or inanimate under study in any statistical investigation.
It is thus a collection of individuals or of their values or of the results of
operations which can be numerically specified.
Finite
and Infinite Population
A population containing a finite number of
objects or items is known as finite population. For example, the students in a
college, the population of a city.
A
population having an infinite number of objects or with the number of objects so
large as to appear practically infinite is termed as infinite population. For example,
the population of stars in the sky.
Existent
and Hypothetical Populations
A
population consisting of concrete objects is known as existent population. For
example, the population of book in a library.
If
the population consists of imaginary objects then it is called hypothetical population.
For example, the population of the throws of a die thrown infinite number of
times is hypothetical population
Concept of Sample in Statistics
A
finite subset of population, selected from it with the objective of investigating
its properties is called a sample. A sample is a representative part of the
population. For example, when we want to study the life of electric bulbs
produced by a company we select some bulbs and study their length of life. This
selected number is the sample.
Size
of the Sample
Number
of sampling units selected from the population is called the size of the
sample. If the size of the sample is small, it may not represent the universe.
If the sample size is very large. It may require more time and money for
investigation.
Characteristics
of a Sample
·
Representativeness
·
Adequacy
·
Un biasedness
·
It should
be optimum
· May not be dependable.
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