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STAB22H3 (122)
Ken Butler (11)


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University of Toronto Scarborough
Ken Butler

STAB22C20 TESTING HYPOTHESES ABOUT PROPORTIONS 2 ExIGNOTShuge pieces of metal that are used as structural parts for cars and planesproblem if they crack while they are manufactured they must be remade or recycled but recycling costs too muchbefore changes were made to manufacturing only 80 free of cracksafter changes 400 ignots were sent for manufacturing and out of which 83 free of cracks has the cracking rate really reduced or was this by chance p531 1 ExIGNOTStreat 400 ignots as random sample recall each random sample has diff prop of cracked ignots bc there is variation from one sample to anotherso we want to know is this 17 due to sampling variability or is it strong enough evidence that the true cracking rate is now really below 202 ExIGNOTSthe above qn and exs below are answered by testing hypotheses about modelsex has the PMs approval rating changed since the last yrex has teenager smoking been reduced in past 3 yrsex is global T decringHYPOTHESES 1 Hypothesesworking models that are adopted temporarilyie used temporarily ExIGNOTSto test whether changes made to manufacturing process really did improve cracking rate assume that it made no differenceso any sort of improvement is really just random fluctuation sampling errornull hypothesis in this context states that prop of cracks really is still 20ie p020NULL HYPOTHESISassumption that there is no real difference between the groupstreatments in comparison and that if there is any sort it is merely due to random fluctuation Sampling error 3 NULL HYPOTHESISdenoted as H0specfies popn model parameter of interest proposes val for that paramtertypically written in this form
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