「Missing data and imputation」の版間の差分
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!Description | !Description | ||
− | ![*Example]<br>A cohort study in which participants report their body weight every week to research center | + | ![*Example]<br>A cohort study in which participants report their body weight every week to research center for 52 weeks in total |
|- | |- | ||
!Missing not at random<br>MNAR | !Missing not at random<br>MNAR | ||
− | |Missing depends on observed data | + | |Missing depends on observed data |
− | | | + | |Some participants intentionally deny to report higher body weights they don't like and only report lower body weights they like |
+ | *Data of those participants are missed because of the values in the variable ''body weight'' themselves | ||
|- | |- | ||
!Missing at randam<br>MAR | !Missing at randam<br>MAR | ||
| | | | ||
− | *Missing | + | *Missing may depend on '''observed data''' but does not depend on ''unobserved data'' |
*Missing can be explained | *Missing can be explained | ||
− | | | + | |15% of female participants deny to report their body weights after the agreement regardless of measured body weights, but only 1% of male deny to report: |
− | *Data of female participants are more likely missed not because of data (body weights) themselves but because female | + | *Data of female participants are more likely missed not because of data (body weights) themselves but because female are more likely reluctant to report their body weights |
− | *In other words, the variable | + | *In other words, values in the variable ''body weight'' themselves do not affect the missing but another variable ''sex'' affects the missing of values in the variable ''body weight'' |
|- | |- | ||
!Missing completely at random<br>MCAR | !Missing completely at random<br>MCAR | ||
| | | | ||
− | *Missing does | + | *Missing does NOT depend on '''observed data''' NOR on ''unobserved data'' |
*Missing occurs purely at random independely from any observed and unobserved data | *Missing occurs purely at random independely from any observed and unobserved data | ||
− | |A participant moves to outside cohort area because of family affair which has nothing to do with the study and is lost to follow up: | + | |A participant moves to outside cohort area because of family affair which has nothing to do with the study and is lost to follow up at the 10th week: |
− | *Data after the move are missed not because of data (body weights) themselves nor because of the participant's unobserved (unmeasured) characteristic | + | *Data after the move are missed not because of data (body weights) themselves, nor because of the participant's unobserved (unmeasured) characteristic related to the study |
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2023年12月10日 (日) 14:17時点における版
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Three mechanisms (assumptions) of data missing
Description | [*Example] A cohort study in which participants report their body weight every week to research center for 52 weeks in total | |
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Missing not at random MNAR |
Missing depends on observed data | Some participants intentionally deny to report higher body weights they don't like and only report lower body weights they like
|
Missing at randam MAR |
|
15% of female participants deny to report their body weights after the agreement regardless of measured body weights, but only 1% of male deny to report:
|
Missing completely at random MCAR |
|
A participant moves to outside cohort area because of family affair which has nothing to do with the study and is lost to follow up at the 10th week:
|