part11 - Public Health 6450 Fall 2011 Andrew Mugglin and...

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Unformatted text preview: Public Health 6450 Fall 2011 Andrew Mugglin and Lynn Eberly Division of Biostatistics School of Public Health University of Minnesota ph6450@biostat.umn.edu Part 11 Review Revisiting Important Concepts Extending the Ideas Behind Hypothesis Tests for Where are we going? Previously: Tests and CIs for : known (use z and , Chapter 6.1-6.2) Tests and CIs for : unknown (use t and s , Chapter 7.1) Errors and power in significance testing (Chapter 6.3-6.4) Current topics: Extending the ideas behind hypothesis tests for Linking tests with CIs (Chapter 6.2) Hypothesis tests for matched pairs (Chapter 7.1) Sample size calculations (not in M,M&C) (Interval estimates and hypothesis testing for the Binomial will be covered in Ch. 8.) Mugglin and Eberly PubH 6450 Fall 2011 Part 11 2 / 21 Review Revisiting Important Concepts Extending the Ideas Behind Hypothesis Tests for Interpretations of a p-value The p-value gives the probability of X being far away from . Suppose we got a test statistic of t = 2 . 7 with df = 18 and p = 0 . 01. Incorrect: The probability that the null hypothesis is true is . 01. Incorrect: The probability of observing t = 2 . 7 when H is true is 0 . 01. Incorrect: The probability of observing such a large X due to chance is 0 . 01. Correct: The probability of observing a test statistic with a value as or more extreme than t = 2 . 7 when H is true is 0 . 01. Correct: The smaller the p-value, the stronger the evidence against H . Mugglin and Eberly PubH 6450 Fall 2011 Part 11 3 / 21 Review Revisiting Important Concepts Extending the Ideas Behind Hypothesis Tests for Significance tests come from rejection rules First, choose and find the z * that cuts off the right-tail AUC: Pr( Z > z * ) = . Then, reject H : = when the test statistic z = X- / n > z * or equivalently when p < . Is p < ? Is z > z * ? D is trib u tio n o f te s t s ta t. z z x D is trib u tio n o f te s t s ta t. z z p - v a lu e D is trib u tio n s u n d e r H : = fo r te s tin g H a : Mugglin and Eberly PubH 6450 Fall 2011 Part 11 4 / 21 Review Revisiting Important Concepts Extending the Ideas Behind Hypothesis Tests for Metabolic changes due to HAART (revisited) Scientific question of interest: Do HIV+ patients who start a treatment regimen including a protease inhibitor (PI) see an increase in their BMI?...
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This note was uploaded on 11/21/2011 for the course PUBH 6450 taught by Professor Andymugglin during the Fall '10 term at Minnesota.

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part11 - Public Health 6450 Fall 2011 Andrew Mugglin and...

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