monfils 418_hypothesis testing2-2014

monfils 418_hypothesis testing2-2014 -...

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Sta$s$cs and research design Chapter 7. Hypothesis tes$ng, and z‐test, review
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Media example: z-test review Return to the example of media violence on aggressive behavior ‐ Does violent content in a video aFect subsequent responding? ‐ 100 subjects saw a video containing considerable violence. ‐ They then free associated to 26 homonyms that had an aggressive & nonaggressive form. e.g. cuF, mug, plaster, pound, sock
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Results‐ Mean number of aggressive free associates = 7.10 (sample mean) Assume that we know that without aggressive video the mean would be 5.65 and the standard devia$on = 4.5 These are popula$on parameters ( μ and σ ) Is 7.10 enough larger than 5.65 to conclude that video aFected results? Media example: z-test review
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Sampling Distribu$on of the Mean We need to know what kinds of sample means to expect if the video has no eFect i. e. What kinds of means can we expect if μ = 5.65 and σ = 4.5? This is the sampling distribu$on of the mean.
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Given a popula$on with mean = μ and standard devia$on = σ , the sampling distribu$on of the mean (the distribu$on of sample means) has a mean = μ , and a standard devia$on = σ / n The distribu$on approaches normal as n , the sample size, increases
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Demonstra$on Let popula$on be very skewed Draw samples of 3 and calculate means Draw samples of 10 and calculate means Plot means (see next 3 slides) Note changes in standard devia$ons, and shapes (What about means?) Cont.
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Parent Popula$on Cont.
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Sampling Distribu$on n = 3 Cont.
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Sampling Distribu$on n = 10 Cont.
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Demonstra$on‐‐cont.
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monfils 418_hypothesis testing2-2014 -...

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