Week4-+Sampling - Week4Sampling 1.Probability sampling...

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Week 4 Sampling 1.Probability sampling 2.Non-probability sampling 3.Sampling(Standard) Error  & Confidence Interval
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#1. Sampling A sample should adequately represent the range of variation in the population . Why Sample? Reduced costs  Speed (time) Can provide more highly accurate measures  than including an  entire population in a study . Sampling in the world - Voting populations: what percentage favors each candidate? - Manufactured goods: what proportion will be defective?
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#2. Census (every 10 years) Complete U.S. Population Year 2000 Census  -Counted more than 280 million  - Cost $6.5 billion - Hired more than 500,000 interviewers to track down those who did not return their  census mail  - A net undercount of over 3 million  - 7.6 million people missed and 4.3. million counted twice (recent immigrants, illegal aliens, homeless, people in temporary housing, those wanting to  be invisible…) - The 50,000 household Current Population Survey  : more accurate than the Census 
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The quality  of the sample is as important as its size How do we assure ourselves that we’re choosing a representative  sample?  (To ensure that the range of variation in the population will be  represented adequately in a sample) The selection process itself is critical! 
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#3. Defining a Population First, Define the population of interest! In what group exactly are you interested? To whom do you want the result of the study to apply? Characteristics of a population Top down (from population to sample)  can be any size  includes all  of the individuals who posses a certain characteristic or set of  characteristics has at least 1 characteristic (sometimes several) that sets it apart from any other  population Examples of Populations All Rutgers students  All Rutgers undergrad  students  All Rutgers undergrad  female students All Rutgers undergrad female students who major in science
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#4. Type of Population: Target population: to which the researcher would like to generalize the results? - Specify the criteria (characteristics) for determining which cases are included in the  population and which cases are excluded. Ex. the National Educational Longitudinal Study (2002) - Goal: analyze the relationship between extracurricular activities and academic  achievement - Target population (1998): students enrolled in “all public and private schools containing  eighth grades in the fifty states and District of Columbia”  If unit of analysis is groups or organization: Ex. a social service agencies with staffs of ten or more in a large mid-western city
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#5. Sampling Frame The set of all cases from which the sample is actually selected.
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This note was uploaded on 11/20/2011 for the course SOCIOLOGY 920:311 taught by Professor Phillips during the Fall '10 term at Rutgers.

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Week4-+Sampling - Week4Sampling 1.Probability sampling...

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