Lecture Slides Feb 8

# Lecture Slides Feb 8 - Slide 1 Polling Details and How Data...

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Unformatted text preview: Slide 1 Polling Details and How Data are Used POLS107 February 8, 2010 Professor Jackson ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 2 Who Uses Polling Data? Politicians: candidates, presidents Media Government agencies (federal, state, local) Interest Groups Academic Researchers – explanatory research, secondary analysis of NES, GSS, agency data, etc. ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 3 Definition of Terms Population : the set of people we want information about Sample : a subset of the population selected for analysis Representative sample : a sample that accurately reflects the specified population ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 4 Random = Good Random sample : a sample selected so that every person in the population has an equal probability (chance) of being chosen ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 5 Random Sampling: An Illustration How many balls of each color are there in this “population”? ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 6 How much error? There is ALWAYS some degree of error with any sample Two types of error – Random error (OK) – Systematic error (BAD) How can we estimate the degree of error? ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 7 “Confidence Level” and Margin of Error Refers to statistical probability that the population value falls within a specified range (margin of error) 95% confidence level most common – 95% of the time, the TRUE value is within the margin of error – 5% of the time, it is outside the margin of error ___________________________________...
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• '10
• Jackson,Melinda
• Government, Media, representative, ___________________________________ ___________________________________, ___________________________________ ___________________________________ ___________________________________

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Lecture Slides Feb 8 - Slide 1 Polling Details and How Data...

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