PS102Lecture18

# PS102Lecture18 - + Statistical Inference and Hypothesis...

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+ Statistical Inference and Hypothesis Testing Political Science 102 Introduction to Political Inquiry Lecture 18

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+ Hypothesis Testing Procedures
+ Factors Influencing Statistical “Significance”

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+ Errors in Hypothesis Testing In selecting threshold for judging statistical significance, we should balance the costs of type I and type II errors Standard scientific practice is to set threshold for rejecting H0 at 95% (i.e. .05 level) Assumes type II errors are preferable (a conservative standard) Other thresholds may be more appropriate for different problems or applications
+ Is it a Toss Up?

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+ Hypothesis Tests and Sampling Distributions Hypothesis tests depend on estimated confidence intervals for the parameter Confidence interval depends on sampling distribution of the statistic Distributions of variables may differ substantially and idiosyncratically Seems to make problem intractable But we want the sampling distribution of the mean (or some other estimator statistic) NOT sampling distribution of parent variable
+ Calculating Confidence Intervals Central Limit Theorem tells us: Sum of a set of random variables approaches a normal distribution as n approaches ∞ Normal distribution is the “bell curve” The mean (and other sample statistics) are sums of random variables

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## PS102Lecture18 - + Statistical Inference and Hypothesis...

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