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A finite subset of statistical individuals defined in

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Unformatted text preview: on chosen from the population. A finite subset of statistical individuals defined in a population is called a sample. The number of units in a sample is called the sample size. Sampling unit: The constituents of a population which are individuals to be sampled from the population and cannot be further subdivided for the purpose of the sampling at a time are called sampling units. For example, to know the average income per family, the head of the family is a sampling unit. To know the average yield of rice, each farm owner’ s yield of rice is a sampling unit. Sampling frame: For adopting any sampling procedure it is essential to have a list identifying each sampling unit by a number. Such a list or map is called sampling frame. A list of voters, a list of house holders, a list of villages in a district, a list of farmers etc. are a few examples of sampling frame. 2.3.2 Reasons for selecting a sample: Sampling is inevitable in the following situations: 1. Complete enumerations are practically impossible when the population is infinite. 2. When the results are required in a short time. 3. When the area of survey is wide. 4. When resources for survey are limited particularly in respect of money and trained persons. 5. When the item or unit is destroyed under investigation. 2.3.3 Parameters and statistics: We can describe samples and populations by using measures such as the mean, median, mode and standard deviation. When these terms describe the characteristics of a population, they are called parameters. When they describe the characteristics of a sample, they are called statistics. A parameter is a characteristic of a population and a statistic is a characteristic of a sample. Since samples are subsets of population statistics provide estimates of the 13 parameters. That is, when the parameters are unknown, they are estimated from the values of the statistics. In general, we use Greek or capital letters for population parameters and lower case Roman letters to denote sample statistics. [N, µ, σ, are the sta...
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