Agriculture Reference
In-Depth Information
6
Sampling Design
Collecting quality information/data is a prerequisite
of any research program. And there are mainly
two different methods of
(infinite population). Thus, we need to have a
proper sample following a statistical technique
so as to obtain valid inference about population
characteristics based on sample observations and
avoid taking any wrong decision.
Sampling theory can be visualized as consisting
of three major components: (a)
collecting data:
census method
sample survey
(a)
and (b)
method
. In census method, data are collected
from individual members of the population. On
the other hand, in sample survey method, infor-
mation is collected from the units of sample
drawn for the purpose following definite
methods of the sampling techniques. A com-
parative account of two methods of data col-
lection is given in Table
6.1
.
Research is pursuit towards knowing the
unknowns in this universe. In doing so, it is not
possible to take care of all the aspects; rather
the researchers quite often select only a few
aspects from this universe as the purpose of
study. In most of the research studies, the usual
approach is to generalize the findings, that
is, to draw inference about the population
characteristics based on sample characteristics.
The whole process depends heavily on the
success of drawing sample from the population.
If the sample(s) drawn is not a proper represen-
tative part of the population, then it may lead to
wrong decisions with regard to generalization of
the findings. To avoid this problem, we may
think of checking the whole population, that is,
each and every member of the population. This is
simply not possible, mainly because of time,
labor, cost involvement, and other difficulties.
Sometimes, it is not possible also to identify
each and every member of
selection of proper
sample
,(b)
collection of information from the
sample
analysis of information to draw
inferences about the population as a whole
, and (c)
. Before
discussing the above three components, let us have
a look into the definitions and characteristics of
some of the terminologies related to this aspect.
Population
: A population is a collection or
totality of well-defined objects (entities). The
observations or entities could be anything like
persons, plants, animals, and objects (like nut
bolts, books, pens, pencils, medicines, and
engines). An individual member of the population
is known as
element or unit
of the population.
) is generally referred to as
the number of observations in the population.
Depending upon the size of the population, a
population may be finite or infinite.
Population size
(
N
A finite pop-
ulation
is a population that contains a finite num-
ber of observations, for example, the population
of students in a particular university and popula-
tion of books/journals in a library.
An
is a population that
contains an infinite number of observations
or units or elements, for example, the number
of hairs in a particular head and the number of
plants in a forest.
infinite population
the population
