Table 2 Characteristics of the determinants of (and) the statistical methods used for analysing the primary outcomes in cluster trials

Closed cohort follow-up

76

88

Open cohort follow-up

4

5

Cross-sectional

4

5

Repeated cross-sectional

2

2

Continuous

63

63

Binary

28

28

Counts

5

5

Time to event

2

2

Percentage

2

2

Cluster-level analysis:

 Standard generalized linear model

2

2

Individual-level analysis:

 Generalized linear mixed model

80

80

 Robust standard errors

7

7

 Generalized estimating equations

6

6

Clustering not accounted for:

 Statistical hypothesis test statistic—chi-square

1

1

  Standard generalized linear model

4

4

Linear regression

57

57

Logistic regression

25

25

Analysis of covariance

6

6

Relative sensitivity

1

1

Negative binomial regression

2

2

Analysis of proportions

1

1

Cox Proportional Hazards model

2

2

Poisson regression

4

4

Weibull regression model

1

1

Chi-square test

1

1

Random intercept

76

95

Shared frailty

1

1

Random intercept and slope (repeated measures)

3

4

Exchangeable correlation

5

83

Correlation structure not reported

1

17