InferenceTestofDifferenceofMeansAnderson5：推理測試方式的差異課件

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

2、sample does not influence the selection of the other sample第4頁，共22頁。So if we want to estimate the difference in means between two populations.The point estimate is: So 第5頁，共22頁。For the difference of means what is the standard deviation?第6頁，共22頁。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頁，共22頁。So what is the z-score for the difference in boys and girls pulse rates?第8頁，共22頁。Remember: Use t test if is unknownT-Test statisticUse boxplot to check for normal if samples are small &

4、 data given.第9頁，共22頁。So is there a difference between boys and girls?第10頁，共22頁。Assumptions:第11頁，共22頁。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頁，共22頁。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頁，共22頁。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頁，共22頁。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頁，共22頁。Test StatisticObtain a P-valueP-value = tcdf (7.81, ., 620)*2 0第16頁，共22頁。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頁，共22頁。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頁，共22頁。The Formula Sheet第19頁，共22頁。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