Bài giảng tối ưu hóa Bài 3 Ttest (phần 2) Ph.D Lê Minh Tâm

Chapter 12: t-test Tâm Minh Lê 5/21/2019 Chapter 12: t-test Tâm Minh Lê 5/21/2019 William Sealy Gosset (1876 - 1937) Chapter 12: t-test Tâm Minh Lê 5/21/2019 Thicker tails and larger standard deviation Chapter 12: t-test Tâm Minh Lê 5/21/2019 when df is large, the curve approaches the normal distribution The reason for that is: when n is increased, the estimated standard error will not fluctuate as much between samples Chapter 12: t-test Tâm Minh Lê 5/21/2019 Chapter 12: t-test Tâm Minh Lê 5/21/2019 Chapter 12: t-test Tâm Minh Lê 5/21/2019 Chapter 12: t-test Tâm Minh Lê 5/21/2019 Chapter 2: Correlation and Regression Tâm Minh Lê 5/21/2019 10 The z-test assumes that: The t-test assumes that: • The numerator varies from one sample to another • The numerator varies from one sample to another • The denominator is constant (from one sample to another) • The denominator varies from one sample to another The sampling distribution of z derives from the sampling distribution of the mean The sampling distribution of t is broader than the sampling distribution of the mean The sampling distribution of t changes with degree of freedom Chapter 12: t-test Tâm Minh Lê 5/21/2019 72 Chapter 12: t-test Tâm Minh Lê 5/21/2019 73 Chapter 12: t-test Tâm Minh Lê 5/21/2019 74 Chapter 12: t-test Tâm Minh Lê 5/21/2019 75 Chapter 12: t-test Tâm Minh Lê 5/21/2019 76 Chapter 12: t-test Tâm Minh Lê 5/21/2019 77 Variance Standard deviation Standard error Chapter 12: t-test Tâm Minh Lê 5/21/2019 78 • The population standard deviation: • The sample standard deviation: Chapter 12: t-test Tâm Minh Lê (unknown) (known) 5/21/2019 79 Chapter 12: t-test Tâm Minh Lê 5/21/2019 80 Assumptions Chapter 12: t-test Tâm Minh Lê 5/21/2019 81 Research question Do smokers and non-smokers differ in terms of their lung capacity ? Chapter 12: t-test Tâm Minh Lê 5/21/2019 82 Checking assumptions Chapter 12: t-test Tâm Minh Lê 5/21/2019 83 Chapter 12: t-test Tâm Minh Lê 5/21/2019 84 Chapter 12: t-test Tâm Minh Lê 5/21/2019 85 Chapter 12: t-test Tâm Minh Lê 5/21/2019 86 ... Tâm Minh Lê 5/21/2019 42 Chapter 12: t-test Tâm Minh Lê 5/21/2019 43 Chapter 12: t-test Tâm Minh Lê 5/21/2019 44 Chapter 12: t-test Tâm Minh Lê 5/21/2019 45 Chapter 12: t-test Tâm Minh. .. t-test Tâm Minh Lê 5/21/2019 13 Set the criterion: α= df = Chapter 2: Correlation and Regression Tâm Minh Lê 5/21/2019 14 Collect sample data 0.5 93 0.142 0 .32 9 0.691 0. 231 0.7 93 0.519 0 .39 2 0.418... 12: t-test Tâm Minh Lê 5/21/2019 36 Interpret results Chapter 12: t-test Tâm Minh Lê 5/21/2019 37 Preliminary step: checking assumptions Chapter 12: t-test Tâm Minh Lê 5/21/2019 38 Assumptions