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2 a random sample is in general a representative

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Unformatted text preview: olely on chance . 2. A random sample is in general a representative sample for a homogenous population. 3. There is no need for the thorough knowledge of the units of the population. 4. The accuracy of a sample can be tested by examining another sample from the same universe when the universe is unknown. 5. This method is also used in other methods of sampling. Limitations: 1. Preparing lots or using random number tables is tedious when the population is large. 2. When there is large difference between the units of population, the simple random sampling may not be a representative sample. 3. The size of the sample required under this method is more than that required by stratified random sampling. 4. It is generally seen that the units of a simple random sample lie apart geographically. The cost and time of collection of data are more. 2.5.2 Stratified Random Sampling: Of all the methods of sampling the procedure commonly used in surveys is stratified sampling. This technique is mainly used to reduce the population heterogeneity and to increase the efficiency of the estimates. Stratification means division into groups.In this method the population is divided into a number of subgroups or strata. The strata should be so formed that each stratum is homogeneous as far as possible. Then from each stratum a simple random sample may be selected and these are combined together to form the required sample from the population. Types of Stratified Sampling: There are two types of stratified sampling. They are proportional and non-proportional. In the proportional sampling 19 equal and proportionate representation is given to subgroups or strata. If the number of items is large, the sample will have a higher size and vice versa. The population size is denoted by N and the sample size is denoted by ‘ n’ the sample size is allocated to each stratum in such a way that the sample fractions is a constant for each stratum. That is given by n/N = c. So in this method each stratum is represented a...
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