ch7_Vnotes

# ch7_Vnotes - Chapter 7...

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Sampling distribution of mean becomes almost normal. As sample size gets large enough, ( n   30) . .. Chapter 7 Sampling and Sampling Distributions Outline: Simple Random Sampling Point Estimation Introduction to Sampling Distributions Sampling Distribution of Sample Mean Sampling Distribution of Sample Proportion Statistical Inference Purpose: To obtain information about a population from information contained in a sample. Terminology Review: 1. A population is the set of all the elements of interest. 2. A sample is a subset of the population. 3. A parameter is a numerical characteristic of population. 4. A sample statistic is a sample characteristic. The value is used to estimate the value of the population parameter. 1

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The sample results provide only estimates of the values of the population characteristics. With proper sampling methods, the sample results will provide “good” estimates of the population characteristics.Simple Random Sampling: (I) Finite Population: A simple random sample from a finite population of size N is a sample selected such that each possible sample of size n has the same probability of being selected. Sampling with replacement -- Replace each sampled element before selecting subsequent elements. Sampling without replacement is the procedure used most often. < In large sampling projects, computer-generated random numbers are often used to automate the sample selection process.> (II) Infinite Population: A simple random sample from an infinite population is a sample selected such that the following conditions are satisfied. 1. Each element selected comes from the same population. 2. Each element is selected independently. Comment: 2 2
The population is usually considered infinite if it involves an ongoing process that makes listing or counting every element impossible. 3

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Point Estimation: In point estimation we use the data from the sample to compute a value of a sample statistic that serves as an estimate of a population parameter. We refer to: as the point estimator of the population mean µ . s
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## This note was uploaded on 02/04/2011 for the course MGMT 305 taught by Professor Priya during the Spring '08 term at Purdue.

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ch7_Vnotes - Chapter 7...

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