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Table 3 Reporting of variables imputed in articles using multiple imputation

From: The rise of multiple imputation: a review of the reporting and implementation of the method in medical research

  Type of studies  
Characteristics reported Trials Observational studies All studies
  N (%)* N (%)* N (%)*
  (n = 73) (n = 30) (n = 103)
Variables imputed    
Variables imputed specified/available 61 (84) 28 (93) 89 (86)
Number of variable(s) imputed    
   1 31 8 39
   2 9 7 16
   >2 17 10 27
   Uncleara 4 3 7
Outcome variable imputed    
   Yes 55 (75) 9 (30) 64 (62)
   Not stated 12 (16) 2 (7) 14 (14)
   No 6 (8) 19 (63) 25 (24)
Type of outcome variable imputed    
   Numerical 31 6 37
   Categorical 16 2 18
   Numerical and categorical 8 1 9
Number of imputed outcome variables    
   1 30 6 36
   2 10 1 11
   >2b 12 2 14
   Uncleara 3 0 3
Covariate imputed    
   Yes 13 (18) 21 (70) 34 (33)
   Not stated 12 (16) 2 (7) 14 (14)
   No 48 (66) 7 (23) 55 (53)
Type of covariates imputed    
   Numerical 6 4 10
   Categorical 3 8 11
   Numerical and categorical 3 8 11
   Uncleara,c 1 1 2
Number of imputed covariates    
   1 6 3 9
   2 2 7 9
   >2 5 8 13
   Uncleara 1 3 4
  1. *Unless otherwise stated.
  2. aAuthors provided a generic statement regarding the imputed variables (e.g. the missing data in the covariates were imputed), and did not explicitly specify which outcome or covariate with missing data was imputed, so the number or type of imputed variables could not be verified.
  3. bOne article [128] imputed missing data in 5 incomplete variables for two questionnaires recorded at 6 different waves of data collection (i.e. 60 imputed variables).
  4. cIn one paper [98], the use of MI for imputing missing data in the covariates was derived from the cited reference, so the data type of imputed variables was not clear.