Biostatistics for Radiologists (eBook)

Foreword 6
Preface to the Italian Edition 7
Preface to the English Edition 12
Acknowledgements 13
Contents 14
Introduction 14
1. Diagnostic Performance 14
2. Variables and Measurement Scales, Normal Distribution, and Confidence Intervals 14
3. Null Hypothesis, Statistical Significance and Power 15
4. Parametric Statistics 15
5. Non-Parametric Statistics 15
6. Linear Correlation and Regression 16
7. Reproducibility: Intraobserver and Interobserver Variability 16
8. Study Design, Systematic Reviews and Levels of Evidence 16
9. Bias in Studies on Diagnostic Performance 17
10. How to Write a Radiologic Paper 17
Subject and Noun Index 17
Introduction 18
Evidence-Based Medicine (EBM) 18
Delayed Diffusion of EBM in Radiology and Peculiar Features of Evidence-Based Radiology 22
Health Technology Assessment in Radiology and Hierarchy of Studies on Diagnostic Tests 24
Why do we Need Biostatistics? 28
The Structure of this Book 30
References 32
1 Diagnostic Performance 35
1.1. The Results of an Examination Compared to a Reference Standard 36
1.2. Measures of Diagnostic Performance 37
1.3. Sensitivity, Specificity, FN Rate and FP Rate 38
1.4. Predictive Values, Diagnostic Accuracy and Disease Prevalence 41
1.5. Bayes’ Theorem, Likelihood Ratios and Graphs of Conditional Probability 48
1.6. Cutoff and ROC Curves 52
References 56
2 Variables and Measurement Scales, Normal Distribution, and Confidence Intervals 57
2.1. Variables and Measurement Scales 58
2.2. Gaussian Distribution 61
2.3. Basics of Descriptive Statistics 67
2.4. Standard Error of the Mean 72
2.5. Standard Error of the Difference between Two Sample Means 75
2.6. Confidence Intervals 77
2.7. Confidence Interval of a Proportion 79
References 80
3 Null Hypothesis, Statistical Significance and Power 82
3.1. Null Hypothesis and Principle of Falsification 83
3.2. Cutoff for Significance, Type I or a Error and Type II or ß Error 85
3.3. Statistical Power 86
3.4. Why 0.05? 89
3.5. How to Read a p Value 90
References 91
4 Parametric Statistics 92
4.1. The Foundations of Parametric Statistics 93
4.2. Comparison between Two Sample Means: Student’s t Test 95
4.3. Comparing Three or More Sample Means: the Analysis of Variance 101
4.4. Parametric Statistics in Radiology 106
References 107
5 Non-Parametric Statistics 108
5.1. One Sample with Two Paired Measurements 109
5.2. Two Independent Samples 116
5.3. Three or More (k) Dependent Samples4 118
5.4. Three or More (k) Independent Samples5 119
5.5. Some Considerations Regarding Non-Parametric Tests 121
References 122
6 Linear Correlation and Regression 124
6.1. Association and Causation 124
6.2. Correlation between Continuous Variables 126
6.3. Interpreting the Correlation Coefficient 128
6.4. Test for Significance 130
6.5. Rank Correlation 131
6.6. Linear Regression 133
6.7. Interpreting the Regression Line 137
6.8. Limitations of the Use of the Regression Line 139
References 139
7 Reproducibility: Intraobserver and Interobserver Variability 140
7.1. Sources of Variability 140
7.2. Why do we Need to Know the Variability of Measurements? 143
7.3. Intraobserver and Interobserver Variability for Continuous Variables: the Bland-Altman Analysis 144
7.4. Interpreting the Results of Bland-Altman Analysis 149
7.5. Intra- and Interobserver Variability for Categorical Variables: the Cohen k 151
References 155
8 Study Design, Systematic Reviews and Levels of Evidence 156
8.1. Phases 1, 2, 3, and 4 of Pharmacologic Research 157
8.2. Study Classification 159
8.3. Experimental Studies and Control Group 160
8.4. Observational Studies 163
8.5. Randomized Controlled Studies: Alternative Approaches 164
8.6. Studies on Diagnostic Performance: Classification 165
8.7. Randomization and Minimization 168
8.8. Sample Size 170
8.9. Systematic Reviews (Meta-analyses) 174
8.10. Levels of Evidence 175
References 178
9 Bias in Studies on Diagnostic Performance 180
9.1. Classification 181
9.2. Bias Affecting External Validity 182
9.3. Bias Affecting Internal Validity 190
9.4. A Lot of Work to Be Done 193
References 194
10 How to Write a Radiologic Paper 195
10.1. Major Papers, Minor Papers, Invited Papers 196
10.2. Which Medical Journal? 198
10.3. Do We Always Need Institutional Review Board Approval and Informed Consent? 215
10.4. Title, Running Title and Title Page 216
10.5. Four-section Scheme, Section Size and Editing Sequence 217
10.6. «Introduction»: Why did you do It? 218
10.7. «Materials and Methods»: What did you do and how did you do it? 219
10.8. «Results»: What did you Find? 223
10.9. «Discussion»: What is the Meaning of your Findings? 224
10.10. «References» 225
10.11. «Abstract» and «Keywords» 226
10.12. Shared Rules 227
10.13. Other Recommendations 227
10.14. Dealing with the Editor’s Response and the Reviewers’ Opinions 229
10.15. To Conclude 232
References 233
Subject and Noun Index 234