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# Section3.1posted - 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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Broad outline of the course Chapters 1-2:   Exploratory data analysis 1 variable (quant. or cat.), 2 variables (quant.) Chapter 3:   Producing data   for inference Observational studies, including  sample surveys Experiments Chapters 4-5:   Properties of data from  randomized experiments and sample  surveys probability theory  sampling distributions Chapters 6-end:   Statistical inference
Chapter 3   Producing data Introduction: types of study (Observational study  vs.  controlled  experiment) 3.1 Design of experiments 3.2 Design of sample surveys 3.3 Toward statistical inference 3.4 Ethics (not covered – read on your own)

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Chapter 3  Introduction:   Sources of  data Anecdotal data Available data Observational studies  and  experiments Data from both include values of explanatory  and response variables for a number of  subjects. The difference:  in an  experiment,   the values  of one or more of the explanatory variables  are  controlled  by the experimenter.
Chapter 3  Introduction: Experiments  vs.  observational  studies Examples 3.4 and 3.5, p. 176 : 1364 children, followed from infancy through 6 th   year in school Explanatory:  amount of time spent in child care,  ages 0 – 4.5 Response:  adults’ ratings on several behavioral  scales (cooperativeness, aggressiveness,  obedience) Results:  the more time spent in child care, the  more they were rated as uncooperative,  aggressive, disobedient, etc. (i.e., positive  associations)

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Chapter 3  Introduction: Experiments  vs.  observational  studies Examples 3.4 and 3.5, p. 176 : This was an  observational study  and not a  controlled experiment .   Lurking variables? An experiment was probably impossible here.   But if an experiment  had  been possible: How would it have proceeded? Why would it have helped decide whether there is  causation between child care and behavioral  problems?
Sample surveys are an important kind of  observational study . Take a  sample  from a  population  and measure the  values of explanatory and response variables  (usually categorical). Examples: Explanatory:  political affiliation (R, D, I).  Response:   opinion on effectiveness of President  (i.e., typical public- opinion poll) Explanatory:  socioeconomic status.  Response:  marital  status Explanatory:  type of TV program preferred (news, sports,  reality, etc.).  Response:  bought product or not Chapter 3  Introduction:   Sample  surveys

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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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Section3.1posted - STOR155,Section2 Thursday,February18...

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