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# April 11 - parameter A 95 CI means we use an alpha of.05...

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April 11, 2008 Introduction to inferential statistics April 11-16 o I. Alpha: the critical region of a probability distribution o II. Confidence intervals o III. The t-distribution o IV. Testing a hypothesis about a single population mean I. Alpha: the critical region of a probability distribution o Cases rarely fall in the outer regions of the probability distribution o We establish a standard for an “unlikely” result o The is alpha: out critical region II. Confidence Intervals o Statistical inferences are uncertain – a confidence interval captures the extent of uncertainty o It’s an interval within which we are confident the actual population value lies – bracketed by alpha o Normally, we use a 95% CI We are 95% confident that our range includes the true population

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Unformatted text preview: parameter A 95% CI means we use an alpha of .05, with 5% risk of Type I error II. Calculating Confidence Intervals o CI = ± z x (s/ n ) o If alpha = .05, z α =1.96 – this is a 95% CI o If alpha = .01, z α =2.58 – this is a 99% CI o To find z α , we look in table E-2 for the z score that corresponds to α/2 o Ex. II. Confidence intervals o The confidence interval is a range (negative and positive) around our sample statistic o How many standard errors we go out from the statistic depends on the confidence level we select o To increase out confidence in out interval, use a larger CI or a larger sample o...
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April 11 - parameter A 95 CI means we use an alpha of.05...

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