9/27/2010
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Point and Interval Estimation
1
Review
• Inferential statistics are concerned with
forming inferences that extend beyond the
immediate sample data to make
conclusions about unknown parameters in
the larger population
• Sample statistics are estimated to provide
the best numerical summary of any
particular aspect in the population
2
Review
• The goal of inferential statistics is to make
generalizations from sample statistics to
population parameters
– Thus if all population parameters are known,
inferential statistics are not needed
• Most social science research does not
have population level information
however… just observations from samples
3
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2
Statistical Estimation
• Process of using known sample statistics
to make educated guesses about value of
unknown population parameters
• The goal of statistical point estimation is to
find and identify the right parameter as
accurately as possible given a model (i.e.,
a function) applied to the sample data
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Point Estimation
• Estimate a single best number (the sample
statistic) to gauge the value of a
population parameter
– e.g. estimate the population mean by using
the sample mean, and/or estimate the
population standard deviation by using the
sample standard deviation
• Gives no information about how close the
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 Spring '10
 Fairchild
 Statistics, Normal Distribution, Standard Deviation

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