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Unformatted text preview: Sampling and Point Estimation GE331 / IE300 G. Kksal UIUC, IESE, 2011 2 Contents Simple random sampling Point estimator vs. point estimate Accuracy vs. precision Sampling distributions Some properties of estimators Mean squared error Standard error Methods of point estimation: Maximum likelihood method Some other methods of sampling 3 Sampling and Estimates The reason we select a sample is to collect data to answer a research question about a population. The sample results provide only estimates of the values of the population characteristics. With proper sampling methods, the sample results can provide good estimates of the population characteristics. 4 Sampling From a Finite Population Finite populations are often defined by lists such as: Credit card account numbers Inventory product numbers Class membership roster A simple random sample of size n 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. 5 Sampling From a Finite Population Replacing each sampled element before selecting subsequent elements is called sampling with replacement. Sampling without replacement is the procedure used most often. In large sampling projects, computergenerated random numbers are often used to automate the sample selection process. 6 Sampling From a Finite Population Example: A simple random sample of 10 students from the Engineering College undergraduates of 6628 students can be selected as follows: 1. Assign a random number to each of the 6628 students generated using Excels RAND function (U(0,1)) 2. Select the 10 applicants corresponding to the 10 smallest random numbers. 7 Sampling From an Infinite Population Populations are often generated by an ongoing process where there is no upper limit on the number of units that can be generated. Some examples of ongoing processes, with infinite populations, are: parts being manufactured on a production line transactions occurring at a bank telephone calls arriving at a call center customers entering a store 8 Sampling From an Infinite Population A random sample from an infinite population is a sample selected such that the following...
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This note was uploaded on 01/26/2012 for the course IE IE 300 taught by Professor Zafarani during the Spring '09 term at University of Illinois, Urbana Champaign.
 Spring '09
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