Aviva Petrie is Honorary Associate Professor, Biostatistics Unit, UCL Eastman Dental Institute, London, UK.

Caroline Sabin is Professor of Medical Statistics and Epidemiology, Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London, UK.

Preface ix

Part 1 Handling data 1

1 Types of data 2

2 Data entry 4

3 Error checking and outliers 6

4 Displaying data diagrammatically 8

5 Describing data: the 'average' 10

6 Describing data: the 'spread' 12

7 Theoretical distributions: the Normal distribution 14

8 Theoretical distributions: other distributions 16

9 Transformations 18

Part 2 Sampling and estimation 21

10 Sampling and sampling distributions 22

11 Confidence intervals 24

Part 3 Study design 27

12 Study design I 28

13 Study design II 31

14 Clinical trials 34

15 Cohort studies 37

16 Case-control studies 40

Part 4 Hypothesis testing 43

17 Hypothesis testing 44

18 Errors in hypothesis testing 47

Part 5 Basic techniques for analysing data 51

Numerical data

19 Numerical data: a single group 52

20 Numerical data: two related groups 54

21 Numerical data: two unrelated groups 57

22 Numerical data: more than two groups 60

Categorical data

23 Categorical data: a single proportion 63

24 Categorical data: two proportions 66

25 Categorical data: more than two categories 69

Regression and correlation

26 Correlation 72

27 The theory of linear regression 75

28 Performing a linear regression analysis 77

29 Multiple linear regression 81

30 Binary outcomes and logistic regression 85

31 Rates and Poisson regression 89

32 Generalized linear models 93

33 Explanatory variables in statistical models 96

Important considerations

34 Bias and confounding 100

35 Checking assumptions 104

36 Sample size calculations 107

37 Presenting results 111

Part 6 Additional chapters 115

38 Diagnostic tools 116

39 Assessing agreement 119

40 Evidence-based medicine 124

41 Methods for clustered data 127

42 Regression methods for clustered data 130

43 Systematic reviews and meta-analysis 134

44 Survival analysis 138

45 Bayesian methods 142

46 Developing prognostic scores 144

Appendices 147

A Statistical tables 148

B Altman's nomogram for sample size calculations (Chapter 36) 155

C Typical computer output 156

D Checklists and trial profile from the EQUATOR network and critical appraisal templates 169

E Glossary of terms 178

F Chapter numbers with relevant multiple-choice questions and structured questions from Medical Statistics at a Glance Workbook 188

Index 190