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# Cal Poly STAT 217 - Tests of Significance

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Stat 217 – Day 6Quiz 1 NotesLast TimeExample 1: Helper/HindererIf infants are picking at randomPowerPoint PresentationMickelsonSlide 8“Survey”Data CollectionTo DoStat 217 – Day 6Tests of SignificanceQuiz 1 NotesSolutions posted in PolyLearnGrading notation(c) the question I intended(d) make sure put it in context (“of the time”)Use the percentage or proportionLast TimeUsing observed sample data to evaluate a claim about the general processIs this evidence that students tend to put Tim on the left?Is this evidence that Sarah does better than guessing?Idea: Look at results that do happen “by chance alone” to see whether our observed data are consistent with that patternExample 1: Helper/HindererTrying to decide between1. Infants do evaluate individuals as appealing or aversive based on their actions2. Infants don’t have a genuine preference and these 16 just happened to pick the helper toy more oftenIf infants are picking at randomMeaning equally between the two toys in the long runSmall p-value : It would be very unlikely to have 14 (or more) picking the helper toy if all 16 infants were picking blindly between the two toysConclusion: Strong evidence against the null hypothesis in favor of the alternativeStrong evidence these infants (in the long run) have a genuine preference for the helper toyMickelsonNull hypothesis:  = .418 (his probability of a putt is the same as golfers’ overall)Alternative hypothesis: :  < .418 (Phil has a lower probability of other golfers)MickelsonIf Phil’s probability of a 10-foot putt was .418, we’d expect to see him make 7 or fewer in about 6% of repetitions of 28 putts by chance aloneA p-value of .064 is weak evidence that Phil’s long-run probability of putt is lower than .418.Phil is a “statistically significantly” worse putter.“Survey”A campus legend tells the story of two friends who told their professor that they got a flat tire returning to town and missed the exam. The professor agreed to give them a make-up exam. The first question (worth 5 points) was easy, but the second question worth 95 points, asked “Which tire was it?”Data CollectionIf you have to choose a hypothetically flat tire, which of the four tires would you say went flat?Left front Right frontLeft rear Right rearTo DoReading3 in PolyLearnReading4 in PolyLearnSubmit Lab 1 at beginning of

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