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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.