Section3.2posted

Section3.2posted - STOR155,Section2 Thursday,February18,...

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STOR 155, Section 2 Thursday, February 18,  2010 Chapter 3 Introduction and Section 3.1
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3.2  Sampling design Sample surveys : terminology and basic  ideas Simple random samples Stratified samples Multistage samples Cautions about sample surveys
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3.2  Sampling design:   Terminology Sample survey :  Take a  sample   from a  population  and measure the values of  one or more variables (usually categorical) Typical example:  opinion poll.  (Samping  units are people, variables are opinions.)   Other examples
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3.2  Sampling design: kinds of  design Key questions for a sample survey:   What is the population? What variables are measured? What’s the  design ?  That is, how was the  sample selected? Kinds of design for sample surveys simple random sampling stratified sampling multistage sampling                        Bad kinds of design 
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3.2  Sampling design:   Examples of  bad  designs Convenience sampling – e. g., ask the first 20   people you meet on the street Why bad? Nonrandom sampling by someone with an interest  in the outcome Example 3.22 (technician sampling steel for quality  control) Political organization stops ‘random’ people of the  street to ask opinions Voluntary response samples (worst!!) Example 3.23: American Family Association CNN.com “Quick Vote” or ESPN.com “sportsnation” Ann Landers “poll” of parents:  If you had it to do over  again, would you have children?
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3.2  Sampling design:  
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This note was uploaded on 06/12/2010 for the course STOR 155 taught by Professor Andrewb.nobel during the Spring '08 term at UNC.

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Section3.2posted - STOR155,Section2 Thursday,February18,...

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