Institut für Sozialmedizin Campus Lübeck Missing data due ... file(esp. due to back pain) •...

Institut für SozialmedizinCampus Lübeck

Folie 1 / 15

Missing data due to a ‘checklist-effect’

Dr. Thorsten Meyer1), Dr. Ines Schäfer1), Dr. Christine Matthis1)

Prof. Dr. Thomas Kohlmann2); Dr. Oskar Mittag1)

1) Institute for Social Medicine, University Clinics Schleswig-Holstein, Campus Luebeck2) Institute for Community Medicine, Ernst-Moritz-Arndt-University, Greifswald

acknowledgement‘Die Abschätzung von Rehabedarf bei aktiven Mitgliedern der Gesetzlichen Rentenversicherung: derLübecker Algorithmus und seine Validierung’, A1-project, principal investigator: Prof. Dr. Dr. H. Raspe, Norddeutscher Verbundes für Rehabilitationsforschung, supported by BMBF and VDR (FKZ: 02 1 06)


Folie 2 / 15

Problem…


Folie 3 / 15

…and possible (simple-minded) solutions:

Som = 1.60imputation by individual mean:

Som = 1.15imputation by group mean:

Som = Missingaccording to manual:

Som = 0.67assumption of a „checklist effect“:


Folie 4 / 15

assumption: checklist-effect

In these respondents, all items with missing data in the respectivescale are interpreted as „not at all“-responses.

definition by the following response pattern:

(1) at least one missing value, and (2) at least one valid item response, and (3) no ‘not at all’-responses.


Folie 5 / 15511

3010

1029

11028

000317

3000016

60000025

400000234

6100001103

40000000002

400000000001

0000000000000

number of valid positive

responseswithout

“not-at-all”-responses

121110987654321

number of missing item responses

Number of missing item responses in relation to the number of valid positive responses (‘checklist effect’ highlighted in the diagonal)

somatisation subscale of SCL-90-R


Folie 6 / 15

85,8 % (194)12,4 % (28)

work status blue-collar / manual workerwhite-collar / clerical worker

68,9 % (153)job full-time

78,1 % (178)11,4 % (26)

education secondary school (Hauptschule)secondary school (Realschule)

11,0 % (25)75,4 % (172)11,4 % (26)

2,2 % (5)

family status singlemarried

divorced / separatedwidowed

73,2 % (167)male sex50,1 (SD=6,5) age

• n=228 • primarily blue collar workers who previously

had filed applications for medical rehabilitation benefits(esp. due to back pain)

• postal survey

Sample


Folie 7 / 15

no missing data

checklist-effect

other types of missing data

no valid item responses at all

75%

16%9%0%

somatisation subscaleSCL-90-R

1. prevalence of the checklist-effect?1. prevalence of the checklist-effect?2. stable phenomenon within the questionnaire?


Folie 8 / 15

succeeding items: questions on pain loci


Folie 9 / 15

depression (CES-D)


Folie 10 / 15

no missing data

checklist-effect

other types of missing data

no valid item responses at all

75%

16%9%0%

somatisation subscaleSCL-90-R

1. prevalence of the checklist-effect?2. stable phenomenon within the questionnaire?

83%

11%6%0%

87%

2%10%1%

pain items depressivenessCES-D

• of those subjects with a checklist-effect in the somatisation subscale, 7 out of 10 had a checklist effect in the pain items

• all subjects with a checklist-effect in the painitems had a checklist-effect in thesomatisation subscale, too


Folie 11 / 15

3. Do subjects with the postulated checklist-effect differfrom the other subjects with regard to socialcharacteristics and health status?

No.

F=1.44; dfbetw=2; dfwithin=218 ;p=.239η2=0.013

M=17.1SD=8.8

M=16.3SD=7.7

M=19.9SD=10.6

depression(CES-D, 0-60)

F=0.27; dfbetw=2; dfwithin=212; p=.76η2=0.002

M=39.0SD=17.9

M=37.8SD=21.2

M=36.6SD=19.9

vitality(SF-36, 0-100)

χ2=3.395; df=6; p=.758; VC=.09

2(1.2 %)

30(17.6 %)110 (64.7

%)28

(16.5 %)

1(5.0 %)

4(20.0 %)

11(55.0 %)

4(20.0 %)

0

7(20.6 %)

20(58.8 %)

7(20.6 %)

health status goodsatisfactory

not good

bad

χ2=3.7; df=2p=.154; VC=.13

148b)(86.5 %)

23(13.5 %)

15(75.0 %)

5(25.0 %)

28(75.7 %)

9(24.3 %)

education lowera)

medium or higherc)

F=0.27; dfbetw=2; dfwithin=220; p=.36η2=0.009

M=52,0SD=7,6

M=50,3SD=6,7

M=49,8SD=6,3

age

χ2=2.9; df=2p=.229, VC=.11

125(73.1 %)

12(60.0 %)

30(81.1 %)

Sex male

statistic, degrees of freedom, level of significance, effect size

no missingdata

(n=171)

other missing data

(n=20)

„checklist-effect“(n=37)

test on difference between groups

type of missing data


Folie 12 / 15

4. results of different imputation procedures

0.610.580.620.67sd

0.980.961.041.04mean

10028N missing

227228228200N valid

checklist-effect

ML-estimation

(EM-algorythm)

manual-based +

group mean

manual-based

(max. 4 MD)

imputation

M=.65SD=.37N=27


Folie 13 / 15

-.304n=221

-.370n=221

-.317n=222

-.335n=195

vitality(SF-36)

-.391n=225

-.413n=226

-.373n=226

-.402n=200

functional capacity(FFbH-R)

.446n=215

.436n=216

.425n=216

.437n=193

rumination(PRSS)

.496n=215

.536n=215

.504n=215

.531n=190

depression(CES-D)

checklist-effect

ML-estimation

(EM-algorythm)

manual-based +

group mean

manual-based

(max. 4 MD)

imputation

5. different covariance structures?

Pearson correlation coefficient (all r p<.001)


Folie 14 / 15

Angaben in Prozent

1,4

16,2

30,6

8,7 8,8

13,9

A4-Survey Rehaantragsteller Kurgäste .0

5

10

15

20

25

30

35

Checkliste Sonstige MD

checklist-effect in other surveys


Folie 15 / 15

Discussion and conclusions

Suggestion: Identification of possible checklist-effects in questionnaires+ if present: additional coding of missing values as non-affirmativeresponses

1. assumption of checklist effect accomplished an almostcomplete imputation of missing values based on theory

2. reduction of bias towards inclusion of less ill subjects3. the missingness does not seem to be conditional on some

other variable(s) observed in the data (MAR)4. ML-estimation yielded similar mean and sd, but different

correlations

identification of checklist-effect in other samplesanalyzing validity in methodological studies, e.g. cognitive survey

Institut für Sozialmedizin Campus Lübeck Missing data due ... file(esp. due to back pain) •...

Documents

Transcript of Institut für Sozialmedizin Campus Lübeck Missing data due ... file(esp. due to back pain) •...