InferenceTestofDifferenceofMeansAnderson5：推理测试方式的差异课件

1、Find the mean number of points for the basketball team and the standard deviation.PlayerPointsSt. Dev.John51Tim82Ed124Marcus103Demetrius144第1页，共22页。Inference Test of Difference of MeansSection 11.1第2页，共22页。ExperimentSeparate boys & girls.Take Pulse rates第3页，共22页。Remember.IndependentSelection of one

2、sample does not influence the selection of the other sample第4页，共22页。So if we want to estimate the difference in means between two populations.The point estimate is: So 第5页，共22页。For the difference of means what is the standard deviation?第6页，共22页。The properties of the sampling distribution of If n1 an

3、d n2 are sufficiently large or the populations normal, then the distribution will be approximately normal.第7页，共22页。So what is the z-score for the difference in boys and girls pulse rates?第8页，共22页。Remember: Use t test if is unknownT-Test statisticUse boxplot to check for normal if samples are small &

4、 data given.第9页，共22页。So is there a difference between boys and girls?第10页，共22页。Assumptions:第11页，共22页。D.F. is a little more complicated!A conservative estimate of the P-value can be found by using a df = smaller of either n1-1 or n2-1.第12页，共22页。Lets try one!College financial aid offices expect studen

5、ts to use summer earnings to help pay for college. But how large are these earnings? One large university studied this by asking a random sample of 1296 students who had summer jobs how much they earned. They were then separated into two groups based on gender. Is there a difference in the amount ma

6、les and females earn?第13页，共22页。Amounts different for males & females?nmeanst. dev.Males675$1884.52$1368.37Females621$1360.39$1037.46Parameter:= true mean amount males earned= true mean amount females earned第14页，共22页。HypothesisorAssumptionsRandom: samples chosen randomlyApproximately normal: n130 and

7、 n230.Independent: more than 6750 males and 6210 femalesNameUse a 2 sample T test of means since is unknown第15页，共22页。Test StatisticObtain a P-valueP-value = tcdf (7.81, ., 620)*2 0第16页，共22页。Now to finish it up!Make a decisionState a conclusionReject the Ho since p-value(0) (0.05)Theres sufficient ev

8、idence to support the claim that there is a difference in the amounts earned by males and females.第17页，共22页。Pooling the DataIf you prove the standard deviations are equal then you can pool the data together.You dont want to do this.its another type of hypothesis test to prove standard deviations equalNever Pool!第18页，共22页。The Formula Sheet第19页，共22页。If you bought a used camera in good condition from a friend, would you pay the same as you would if you bought the same item from a stranger. FriendStrang