Primer of Biostatistics

327 Pages·2011·19.58 MB·English

by  Stanton A. Glantz

Primer of Biostatistics
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Primer of Biostatistics
Seventh Edition
Stanton A. Glantz, PhD
Professor of Medicine
American Legacy Foundation Distinguished Professor in Tobacco Control
Director, Center for Tobacco Control Research and Education
Member, Cardiovascular Research Institute
Member, Philip R. Lee Institute for Health Policy Studies
Member, Helen Diller Family Comprehensive Cancer Center
University of California, San Francisco
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To Marsha Kramar Glantz
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What I’ve proposed is that we have a panel of medical experts that are making determina-
tions about what protocols are appropriate for what diseases. There’s going to be some
disagreement, but if there’s broad agreement that, in this situation the blue pill works better
than the red pill, and it turns out the blue pills are half as expensive as the red pill, then we
want to make sure that doctors and patients have that information available to them.
President Barack Obama, 2009*
*Interview with ABC News’ Dr. Timothy Johnson, July 15, 2009.
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Contents
Preface ...........................................................xiii 4. The Special Case of Two Groups:
The t test .................................................49
1. Biostatistics and Clinical Practice ................1
The General Approach .....................................49
What Do Statistical Procedures Tell You? ............3 The Standard Deviation of a Difference
Why Not Just Depend on the Journals? ...............4 or a Sum ....................................................51
Why Has the Problem Persisted? ........................5 Use of t to test Hypotheses About
Two Groups .................................................52
2. How to Summarize Data .............................7
What if the Two Samples Are Not
Three Kinds of Data ..........................................7 the Same Size? ..........................................56
The Mean .........................................................9 Cell Phones Revisited ......................................56
Measures of Variability ......................................9 The t test is an Analysis of Variance ...................59
The Normal Distribution ...................................10 Common Errors in the Use of the t test
Getting the Data .............................................10 and How to Compensate for Them ................60
Random Sampling .......................................10 How to Use t tests to Isolate Differences
Bias ...........................................................12 Between Groups in Analysis of Variance ........62
Experiments and Observational Studies ........13 The Bonferroni t test ...................................62
Randomized Clinical Trials............................14 More on Cell Phones and Rabbit Sperm ........63
How to Estimate the Mean and Standard A Better Approach to Multiple Comparisons:
Deviation from a Sample ...............................15 The Holm t test .......................................64
How Good Are These Estimates? ......................15 The Holm-Sidak t test ..................................65
Percentiles .....................................................19 Multiple Comparisons Against
Pain Associated with Diabetic Neuropathy .....23 a Single Control ..........................................67
Summary ........................................................25 The Meaning of P .....................................................67
Problems ........................................................25 Statistical Versus Real (Clinical) Thinking ......69
Why P < .05? ..............................................70
3. How to Test for Differences between
Problems ........................................................71
Groups ....................................................27
5. How to Analyze Rates and Proportions .......73
The General Approach .....................................27
Two Different Estimates of the Back to Mars ..................................................73
Population Variance .....................................31 Estimating Proportions from Samples ...............75
What is a “Big” F? ...........................................34 Hypothesis Tests for Proportions .......................78
Cell Phones and Sperm ...................................38 The Yates Correction for Continuity ...............79
An Early Study.............................................38 Effect of Counseling on End-of-Life
A Better Control Group.................................40 Planning in Homeless People ...................79
An Experimental Study .................................41 Another Approach to Testing Nominal Data:
Unequal Sample Size ......................................41 Analysis of Contingency Tables .....................80
Two Way Analysis of Variance ...........................44 The Chi-Square Test Statistic .......................81
Problems ........................................................44 The Yates Correction for Continuity ...............84
ix