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D of population n x s are the standard symbol for the

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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 non-sampling 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. Non-sampling errors: In all surveys some errors may occur during collection of actual information. These errors are called Non-sampling 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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