
GERAS1^{c}

GERAS2^{d}


Imputation method

Mean cost (€)

Bias (%)^{e}

SSE

SEE

SEE/SSE

CP

Mean cost (€)

Bias (%)^{e}

SSE

SEE

SEE/SSE

CP


Complete sample

2101

–

64

62

0.97

–

2103

–

60

61

1.02

–

Naïve imputation method

Complete cases

1957

−144 (−7 %)

67

66

0.99

0.38

1689

−414 (−20 %)

52

54

1.04

0.00

Multiple imputation method

MI MCMC

2037

−64 (−3 %)

74

47

0.64

0.70

1969

−134 (−6 %)

77

41

0.53

0.22

Combination of imputation methods

Combination Scenario A^{f}

2044

−57 (−3 %)

71

47

0.66

0.73

1947

−157 (−7 %)

69

41

0.59

0.12

Combination Scenario B^{g}

2296

195 (9 %)

62

49

0.79

0.02

2075

−28 (−1 %)

49

42

0.86

0.87

 Numbers in bold text show the imputation method(s) that perform the best (lowest bias) for each of the two datasets (GERAS1 and GERAS2)
 Abbreviations: CP coverage probability, MAR missing at random, MCAR missing completely at random, MCMC Markov Chain Monte Carlo, MI multiple imputation, MNAR missing not at random, SEE standard error estimate, SSE sampling standard error
 ^{a}1000 simulations and sample size 1497
 ^{b}Data missing for 33 % patients at 18 months: 15 % patients institutionalised, 6 % died, 12 % lost to followup
 ^{c}GERAS1: assumed patients institutionalised were based on a predictive equation (i.e. data MAR)
 ^{d}GERAS2: assumed patients institutionalised if their caregiver time was >470 h/month (i.e. data MNAR)
 ^{e}% bias was calculated as ((estimated−actual)/actual cost × 100), where actual cost was the mean cost for the complete sample
 ^{f}Combination Scenario A: patients lost to followup (data MCAR) had costs imputed using group means method, patients institutionalised (data MAR) were imputed using MI MCMC method (including factors MMSE, ADCSADL and caregiver time), and patients who died (data MAR) had costs imputed using the MI MCMC method (including factors MMSE, patient age and ADCSADL)
 ^{g}Combination Scenario B: same imputation methods as Combination Scenario A, but a fixed cost (€2940 per month) was used for patients who were institutionalised (data MNAR)