Preface |
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xiii | |
Notation |
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xv | |
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Table of cases: Trials used as examples in more than one chapter in the book |
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xviii | |
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1 | (21) |
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1.1 Introduction to randomised trials |
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2 | (1) |
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1.2 Explanatory or pragmatic trials |
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2 | (1) |
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1.3 How does a cluster randomised trial differ from other trials? |
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3 | (6) |
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1.3.1 Recruitment, randomisation and consent |
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4 | (3) |
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1.3.2 Definition of cluster size |
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7 | (1) |
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1.3.3 Analysis and sample size |
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7 | (1) |
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1.3.4 Interventions used in cluster randomised trials |
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8 | (1) |
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1.4 Between-cluster variability |
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9 | (1) |
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1.4.1 Factors that contribute to between-cluster variability |
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9 | (1) |
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1.4.1.1 Geographical reasons |
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9 | (1) |
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1.4.1.2 Individuals choose the cluster to belong to |
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9 | (1) |
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1.4.1.3 Healthcare provided to the cluster |
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9 | (1) |
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1.4.2 Measuring between-cluster variability |
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9 | (1) |
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1.5 Why carry out cluster randomised trials? |
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10 | (3) |
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1.5.1 The intervention necessarily acts at the cluster level |
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10 | (1) |
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1.5.2 Practical and/or ethical difficulties in randomising at individual level |
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10 | (1) |
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1.5.3 Contamination at health professional level |
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11 | (1) |
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1.5.4 Contamination between members of a cluster |
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12 | (1) |
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1.5.5 Cost or administrative convenience |
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12 | (1) |
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1.5.6 Ensuring intervention is fully implemented |
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12 | (1) |
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1.5.7 Access to routine data |
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13 | (1) |
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1.6 Quality of evidence from cluster randomised trials |
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13 | (3) |
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13 | (1) |
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14 | (1) |
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1.6.3 Balancing internal validity, external validity and ethical issues |
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14 | (2) |
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1.7 Historical perspectives |
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16 | (2) |
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1.7.1 Early cluster randomised trials |
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16 | (1) |
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1.7.2 Early cluster randomised trials in health up to 2000 |
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16 | (1) |
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1.7.3 Recent methodological developments |
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17 | (1) |
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1.7.3.1 Methods of analysis |
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17 | (1) |
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17 | (1) |
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1.7.3.3 Estimating the intra-cluster correlation coefficient |
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17 | (1) |
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1.7.3.4 Reporting guidelines |
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17 | (1) |
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1.7.3.5 Recruitment and consent |
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18 | (1) |
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1.7.3.6 Complex interventions |
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18 | (1) |
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18 | (1) |
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18 | (4) |
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19 | (3) |
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22 | (22) |
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2.1 Selecting clusters and participants to enhance external validity |
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22 | (2) |
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22 | (1) |
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23 | (1) |
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2.2 Ethics of cluster randomised trials |
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24 | (11) |
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2.2.1 Components of consent |
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25 | (1) |
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2.2.2 Classification of interventions and implications for individual participant consent |
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25 | (1) |
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2.2.2.1 Individual-cluster interventions |
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25 | (2) |
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2.2.2.2 Professional-cluster interventions |
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27 | (1) |
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2.2.2.3 External-cluster interventions |
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27 | (1) |
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2.2.2.4 Cluster-cluster interventions |
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28 | (1) |
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2.2.2.5 Multifaceted interventions |
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29 | (1) |
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30 | (2) |
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2.2.4 Timing of cluster consent |
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32 | (1) |
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2.2.5 Fully informed consent for educational and awareness campaigns |
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33 | (1) |
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2.2.6 Protecting the privacy of individuals |
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33 | (1) |
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2.2.7 Duty of care to control participants |
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34 | (1) |
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2.2.8 Summary of consent issues |
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35 | (1) |
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2.3 Selection and recruitment of participants to enhance internal validity |
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35 | (6) |
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2.3.1 Trials which identify and recruit individual participants before randomisation (scenario 1) |
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36 | (1) |
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2.3.2 Trials where individual participants are not recruited (scenario 2) |
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37 | (1) |
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2.3.3 Trials where participants are recruited after randomisation but blind to allocation status (scenario 3) |
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38 | (1) |
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2.3.4 Trials where recruitment is carried out after randomisation and where the recruiter knows the allocation (also scenario 3) |
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39 | (1) |
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2.3.5 Identification and recruitment bias: Summary |
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40 | (1) |
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2.4 Retention of participants in the trial |
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41 | (1) |
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41 | (3) |
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41 | (3) |
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3 Designing interventions |
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44 | (16) |
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3.1 Lack of effectiveness of interventions evaluated in cluster randomised trials |
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45 | (1) |
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3.2 What is a complex intervention? |
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46 | (4) |
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3.3 Phases in the development of a complex intervention |
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50 | (1) |
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3.4 Identifying evidence for potential intervention effect (pre-clinical phase) |
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50 | (3) |
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3.5 Understanding more about intervention components (modelling phase) |
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53 | (2) |
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3.6 Developing the optimum intervention and study design (exploratory trial phase) |
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55 | (2) |
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3.7 What is the intervention? |
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57 | (1) |
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58 | (2) |
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58 | (2) |
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4 Pilot and feasibility studies |
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60 | (14) |
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4.1 What is a pilot study? |
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60 | (3) |
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4.1.1 Is there a difference between pilot studies and feasibility studies? |
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61 | (1) |
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4.1.2 Internal and external pilot studies |
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62 | (1) |
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4.2 Reasons for conducting pilot and feasibility studies |
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63 | (6) |
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4.2.1 Piloting randomisation and recruitment |
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63 | (3) |
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4.2.2 Piloting the intervention |
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66 | (2) |
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4.2.3 Acquiring information to help with sample size |
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68 | (1) |
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4.2.4 Refining outcome measures |
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68 | (1) |
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4.3 Designing a pilot or feasibility study |
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69 | (2) |
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4.3.1 Size of pilot study |
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70 | (1) |
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4.3.2 Protocols for pilot studies |
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71 | (1) |
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4.4 Reporting and interpreting pilot studies |
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71 | (1) |
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72 | (2) |
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73 | (1) |
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74 | (25) |
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5.1 Parallel designs with only two arms |
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75 | (10) |
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75 | (1) |
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5.1.2 Completely randomised designs |
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75 | (1) |
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5.1.3 Choosing factors to balance in designs that are not completely randomised |
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76 | (2) |
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78 | (1) |
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5.1.5 Stratified random sampling within clusters |
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79 | (1) |
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79 | (3) |
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5.1.7 Other techniques for balancing factors between trial arms |
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82 | (1) |
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82 | (2) |
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5.1.9 Matched-pair designs |
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84 | (1) |
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5.1.10 Unequal allocation to intervention arms |
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85 | (1) |
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5.2 Cohort versus cross-sectional designs |
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85 | (3) |
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5.3 Parallel designs with more than two arms |
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88 | (4) |
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88 | (1) |
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5.3.2 Trials with one more arm than there are active interventions |
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88 | (1) |
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5.3.3 Full factorial designs |
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89 | (3) |
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5.3.4 Randomisation at cluster and individual level |
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92 | (1) |
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92 | (3) |
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5.5 Further design considerations |
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95 | (1) |
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5.5.1 Pseudo cluster randomisation |
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95 | (1) |
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5.5.2 Stepped wedge designs |
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95 | (1) |
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5.5.3 Equivalence and non-inferiority trials |
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95 | (1) |
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5.5.4 Delayed intervention |
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96 | (1) |
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96 | (3) |
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96 | (3) |
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99 | (38) |
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6.1 Data collection and management |
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99 | (2) |
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6.2 Analysis - an introduction |
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101 | (3) |
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6.2.1 Comparing analyses that do and do not take account of clustering |
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102 | (2) |
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6.2.2 The intra-cluster correlation coefficient |
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104 | (1) |
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6.3 Analyses for two-arm, completely randomised, stratified or minimised designs |
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104 | (20) |
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6.3.1 Analyses that do not allow the inclusion of covariates |
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105 | (2) |
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6.3.2 Analysis allowing for the inclusion of covariates at the cluster level only |
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107 | (2) |
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6.3.3 Analyses allowing for the inclusion of covariates at individual and cluster level |
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109 | (1) |
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6.3.3.1 Introduction to different models |
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109 | (1) |
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6.3.3.2 Continuous outcomes - population-averaged and cluster-specific models |
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110 | (3) |
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6.3.3.3 Continuous outcomes - generalised estimating equations |
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113 | (1) |
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6.3.3.4 Continuous outcomes - mixed effects models |
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114 | (2) |
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6.3.3.5 Continuous outcomes - other methods of analysis |
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116 | (1) |
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6.3.3.6 Continuous outcomes - comparison of methods |
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116 | (1) |
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6.3.3.7 Binary outcomes - population-averaged and cluster-specific models |
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117 | (2) |
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6.3.3.8 Binary outcomes - generalised estimating equations |
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119 | (1) |
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6.3.3.9 Binary outcomes - mixed effects models |
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120 | (2) |
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6.3.3.10 Binary outcomes - other methods of analysis |
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122 | (1) |
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6.3.3.11 Binary outcomes - comparison of methods |
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122 | (1) |
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122 | (2) |
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6.3.3.13 Time-to-event outcomes |
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124 | (1) |
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6.4 Analyses for other designs |
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124 | (5) |
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124 | (1) |
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6.4.2 Parallel trials with more than two arms |
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125 | (3) |
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6.4.3 Crossover, stepped wedge and pseudo cluster randomised designs |
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128 | (1) |
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6.5 Intention to treat and missing values |
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129 | (2) |
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131 | (1) |
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132 | (5) |
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133 | (4) |
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7 Sample size calculations |
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137 | (35) |
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7.1 Factors affecting sample size for cluster randomised designs |
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138 | (4) |
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7.1.1 Measuring between-cluster variation in an outcome variable |
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138 | (1) |
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7.1.2 Definition of cluster size |
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139 | (1) |
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7.1.3 Variability in cluster size |
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140 | (1) |
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7.1.4 Clinically important difference |
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140 | (1) |
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7.1.5 Sample size formulae for individually randomised trials |
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141 | (1) |
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7.2 Calculating sample size using the intra-cluster correlation coefficient |
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142 | (3) |
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7.2.1 Increasing the number of clusters to allow for a clustered design |
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142 | (1) |
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7.2.2 Increasing cluster size to allow for a clustered design |
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143 | (2) |
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7.3 Sample size calculations for rates |
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145 | (1) |
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7.4 Restricted number of clusters |
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146 | (3) |
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7.4.1 Administrative reasons |
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146 | (1) |
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7.4.2 Few clusters are available |
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147 | (1) |
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7.4.3 Cost or other practical difficulties of delivering the intervention |
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147 | (1) |
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7.4.4 Minimum number of clusters required |
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148 | (1) |
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7.5 Trials with a small number of clusters |
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149 | (1) |
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7.5.1 Adjustment to sample size calculations when number of clusters is small |
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149 | (1) |
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7.5.2 Balance between the arms in cluster characteristics |
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149 | (1) |
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7.5.3 Loss of intact clusters |
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150 | (1) |
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7.6 Variability in cluster size |
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150 | (4) |
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7.6.1 Using coefficient of variation in cluster size for estimating sample size |
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151 | (1) |
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7.6.2 Estimating coefficient of variation in cluster size |
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152 | (1) |
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7.6.3 Small clusters arising from incident cases |
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152 | (2) |
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7.6.4 Variable cluster size for rates |
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154 | (1) |
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7.7 Comparison of different measures of between-cluster variability |
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154 | (6) |
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7.7.1 Estimating sample size using between-cluster variance |
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154 | (2) |
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7.7.2 Estimating sample size using between-cluster coefficient of variation in outcome |
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156 | (1) |
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7.7.3 Comparison of measures of between-cluster variability for means |
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156 | (1) |
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7.7.4 Comparison of measures of between-cluster variability for proportions |
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157 | (3) |
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7.8 Matched and stratified designs |
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160 | (6) |
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7.8.1 Matched and stratified designs comparing means |
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161 | (1) |
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7.8.2 Matched and stratified designs comparing proportions |
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161 | (1) |
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7.8.3 Matching correlation |
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162 | (1) |
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7.8.4 Strength of relationship between stratification factors and outcomes |
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163 | (1) |
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7.8.5 Cluster size as a stratification factor in primary care |
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163 | (2) |
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7.8.6 Summary of the effect of stratification on power |
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165 | (1) |
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7.9 Sample size for other designs |
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166 | (3) |
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7.9.1 Unequal numbers in each arm |
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166 | (1) |
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7.9.2 Block randomisation |
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166 | (1) |
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166 | (1) |
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7.9.4 Cohort versus cross-sectional studies |
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166 | (1) |
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7.9.5 More than two intervention arms |
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167 | (1) |
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168 | (1) |
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169 | (1) |
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169 | (3) |
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169 | (3) |
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8 The intra-cluster correlation coefficient |
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172 | (24) |
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173 | (2) |
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8.1.1 Proportion of variance interpretation |
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173 | (1) |
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8.1.2 Pair-wise correlation interpretation |
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174 | (1) |
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8.1.3 Relationship between proportion of variance and pair-wise correlation interpretations |
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174 | (1) |
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8.1.4 Kappa interpretation |
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174 | (1) |
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8.1.5 Interpretation in cluster randomised trials |
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175 | (1) |
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8.2 Sources of ICC estimates |
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175 | (4) |
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8.2.1 ICC estimates from trial reports |
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175 | (1) |
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8.2.2 ICC estimates from lists |
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176 | (2) |
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178 | (1) |
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8.3 Choosing the ICC for use in sample size calculations |
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179 | (6) |
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8.3.1 Single ICC estimate from an existing source |
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180 | (1) |
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8.3.2 Single ICC estimate from pilot study |
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180 | (2) |
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8.3.3 Single ICC estimate based on patterns in ICCs |
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182 | (1) |
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8.3.4 Using more than one ICC estimate from existing sources |
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182 | (1) |
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8.3.5 Baseline or interim sample size calculations |
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183 | (1) |
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8.3.6 Comparing different methods |
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184 | (1) |
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8.3.7 Sensitivity analyses |
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185 | (1) |
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8.4 Calculating ICC values |
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185 | (7) |
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8.4.1 Analysis of variance |
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186 | (1) |
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8.4.2 Pearson product-moment correlation coefficient |
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187 | (2) |
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8.4.3 Mixed effects models |
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189 | (2) |
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8.4.4 Generalised estimating equations |
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191 | (1) |
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191 | (1) |
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192 | (1) |
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193 | (3) |
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193 | (3) |
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196 | (1) |
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197 | (10) |
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197 | (1) |
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198 | (2) |
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200 | (3) |
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9.1.4 Meta-analyses - incorporating cluster randomised trials using the design effect |
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203 | (3) |
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9.1.5 Other methods of incorporating cluster randomised trials in meta-analyses |
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206 | (1) |
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9.1.6 Incorporating stratified and matched trials into a meta-analysis |
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206 | (1) |
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9.1.7 Reporting systematic reviews |
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207 | (1) |
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9.2 Cost effectiveness analyses |
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207 | (5) |
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9.2.1 Cost effectiveness analyses and cluster randomised trials |
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208 | (2) |
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9.2.2 Appropriate methods for cost effectiveness analyses of cluster randomised trials |
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210 | (1) |
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9.2.2.1 Bivariate multilevel models |
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210 | (1) |
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9.2.2.2 Two-stage bootstrap |
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210 | (1) |
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9.2.2.3 Robust variance methods |
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211 | (1) |
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9.2.3 Current state of knowledge and areas for future research |
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211 | (1) |
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212 | (1) |
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213 | (2) |
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215 | (3) |
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215 | (3) |
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218 | (49) |
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10.1 Trial quality and reporting quality |
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218 | (9) |
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10.1.1 Checklists for assessing the quality of cluster randomised trials |
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219 | (2) |
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10.1.2 Consort statement for reporting trials |
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221 | (6) |
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10.1.3 Extension to the Consort statement for cluster randomised trials |
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227 | (1) |
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10.1.4 Other extensions to the Consort statement |
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227 | (1) |
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10.2 Steps to improve trial reporting in the early stages of the trial |
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227 | (3) |
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10.2.1 Trial registration |
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227 | (3) |
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10.2.2 Publication of trial protocol |
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230 | (1) |
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10.3 Reporting randomised trials in journal and conference abstracts |
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230 | (2) |
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10.4 Application of Consort statement to cluster randomised trials |
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232 | (30) |
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10.4.1 Item 1a: Information in title |
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232 | (2) |
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10.4.2 Item 2: Background information |
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234 | (3) |
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10.4.3 Item 3: Trial design |
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237 | (2) |
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10.4.4 Item 4: Description of participants |
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239 | (1) |
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10.4.5 Item 5: Description of interventions |
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239 | (2) |
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241 | (2) |
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10.4.7 Item 7: Sample size and interim analyses |
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243 | (1) |
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10.4.8 Item 8: Generation of random allocation sequence |
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244 | (1) |
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10.4.9 Item 9: Allocation concealment |
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245 | (1) |
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10.4.10 Item 10: Who generated allocation sequence, enrolled participants and assigned participants to their groups |
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245 | (2) |
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10.4.11 Item 11: Blinding |
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247 | (1) |
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10.4.12 Item 12: Statistical methods |
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248 | (1) |
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10.4.13 Item 13: Participant flow |
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249 | (3) |
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10.4.14 Item 14: Recruitment |
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252 | (3) |
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10.4.15 Item 15: Baseline data |
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255 | (2) |
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10.4.16 Item 16: Numbers analysed |
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257 | (1) |
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10.4.17 Item 17: Outcomes and estimation |
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257 | (1) |
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10.4.18 Item 18: Ancillary analyses |
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258 | (1) |
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10.4.19 Item 19: Adverse events |
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259 | (1) |
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10.4.20 Item 20: Limitations |
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260 | (1) |
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10.4.21 Item 21: Generalisability |
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261 | (1) |
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10.4.22 Item 22: Interpretation |
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261 | (1) |
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10.4.23 Other information |
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262 | (1) |
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262 | (5) |
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263 | (4) |
Index |
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267 | |