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Chapter 14

SOAN 3120 Chapter Notes - Chapter 14: Confidence Interval, Sampling Distribution, Standard Deviation

Sociology and Anthropology
Course Code
SOAN 3120
Andrew Hathaway

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Chapter 14-Condence Intervals:
Statistical Inference:
Provides methods for drawing conclusions about a population from sample
Simple conditions for inference about a mean:
oWe have an SRS from the population of interest. This is no nonresponse
or other practical diculty
oThe variable we measure has an exactly normal distribution
N(mu,sigma) in the population
oWe don’t know the population mean, but we do know the population
standard deviation
The Reasoning of Statistical Estimation:
Sampling distribution of XBAR tells us how close to mu the sample mean is
likely to be
Statistical estimated just turns that information around to say how close to
XBAR the unknown population mean is likely to be
We call the interval numbers between the values con*dence intervals for mu
Margin of Error and Condence Level:
Most con*dence intervals look like: estimate (+ over -) margin of error
A level C con*dence interval for a parameter has 2 parts:
oAn interval calculated from the data in the way written above
oA con*dence level C, which gives the probability that the interval will
capture the true parameter value in repeated samples
The con*dence level is the success rate of the method that produces the
We don’t know whether the 95% con*dence interval from a particular sample
is one of the 95% that capture mu or one of the unlikely 5% that miss
Condence Intervals for a Population Mean:
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