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Unformatted text preview: 1 Lecture 9 Introduction to Statistical Inference: The Bootstrap Lecture 9 1 Inference: The Bootstrap Lecture 9 Outline 1. Statistical Inference 2 Data as evidence 2. Data as evidence 3. Frequentist statistical reasoning 4. Bootstrap 5. Measuring precision 6. Bootstrap and confidence interval estimation estimation 7. References 2 2 1. Statistical Inference: Search for “ Truth ” Sampling/Probability Observed Value Truth for for a Population Representative Sample Statistical inference 3 1.1. Statistical Inference: Search for “ Truth ” Sampling/Probability Observed rate in a True survival rate representative in population sample Statistical inference 4 3 1.2 Statistical Inference An approach for using information (data) from the sample to make statements about the population sample to make statements about the population Which population? • The one from which your sample was randomly drawn • The one for which your sample is reasonably thought to be representative reasonably thought to be representative  like a random sample 5 6 4 2. Data as Evidence 2x2 Table Relapse within 400 days; from Figure 1 in Csernansky, et al. 2002 Risp Hal Total Relapse 41 67 108 No 136 121 257 Relapse Total 177 188 365 7 2.1 Observed Relative Rate of Relapse • Risperidone: Relapse rate = 41/177 = 0 23 Risperidone: Relapse rate 41/177 0.23 • Haloperidol: Relapse rate = 67/188 = 0.35 • Relative rate = Risp rate/Hal rate = (41/177) / (67/188) = 0.65 8 5 2.2 Statistical Inference Frequentist Style • Our observed rate is not the population rate! It deviates from the true population value • It deviates from the true population value because we only have a sample of fixed size, not the whole population....
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This note was uploaded on 02/24/2010 for the course BIOS 600 taught by Professor Staff during the Spring '08 term at UNC.
 Spring '08
 Staff

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