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Unformatted text preview: ndard symbols for the size, mean,
S.D, of population. n , x , s, are the standard symbol for the size,
mean, s.d of sample respectively].
2.3.4 Principles of Sampling:
Samples have to provide good estimates. The following
principle tell us that the sample methods provide such good
estimates
1. Principle of statistical regularity:
A moderately large number of units chosen at random from
a large group are almost sure on the average to possess the
characteristics of the large group.
2. Principle of Inertia of large numbers:
Other things being equal, as the sample size increases, the
results tend to be more accurate and reliable.
3. Principle of Validity:
This states that the sampling methods provide valid
estimates about the population units (parameters).
4. Principle of Optimisation:
This principle takes into account the desirability of
obtaining a sampling design which gives optimum results. This
minimizes the risk or loss of the sampling design.
The foremost purpose of sampling is to gather maximum
information about the population under consideration at minimum
cost, time and human power. This is best achieved when the sample
contains all the properties of the population.
Sampling errors and nonsampling errors:
The two types of errors in a sample survey are sampling
errors and non  sampling errors.
1. Sampling errors:
Although a sample is a part of population, it cannot be
expected generally to supply full information about population. So
there may be in most cases difference between statistics and
14 parameters. The discrepancy between a parameter and its estimate
due to sampling process is known as sampling error.
2. Nonsampling errors:
In all surveys some errors may occur during collection of
actual information. These errors are called Nonsampling errors.
2.3.5 Advantages and Limitation of Sampling:
There are many advantages of sampling methods over
census method. They are as follows:
1. Sampling saves time and labour.
2. It results in reduction of cost in terms of money and manhour.
3. Sampling ends u...
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 Winter '08
 Moshiri
 Business

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