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ページの作成:「{{Floating Menu}} ==Three mechanisms (assumptions) of data missing== {|class="wikitable" style="min-width:400px" |+Mechanisms (assumptions) of data missing |- ! !Descrip…」
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==Three mechanisms (assumptions) of data missing==
{|class="wikitable" style="min-width:400px"
|+Mechanisms (assumptions) of data missing
|-
!
!Description
![*Example]<br>A cohort study in which participants report their body weight every week to research center
|-
!Missing not at random<br>MNAR
|Missing depends on observed data themselves
|
|-
!Missing at randam<br>MAR
|
*Missing does not depend on observed data but may depend on unobserved data
*Missing can be explained
|Female participants less likely report their body weights than male participants:
*Data of female participants are more likely missed not because of data (body weights) themselves but because female tend to be reluctant to report their body weights
*In other words, the variable of ''body weight'' itself does 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 does not depend on observed data nor on 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:
*Data after the move are missed not because of data (body weights) themselves nor because of the participant's unobserved (unmeasured) characteristic
|}
==Three mechanisms (assumptions) of data missing==
{|class="wikitable" style="min-width:400px"
|+Mechanisms (assumptions) of data missing
|-
!
!Description
![*Example]<br>A cohort study in which participants report their body weight every week to research center
|-
!Missing not at random<br>MNAR
|Missing depends on observed data themselves
|
|-
!Missing at randam<br>MAR
|
*Missing does not depend on observed data but may depend on unobserved data
*Missing can be explained
|Female participants less likely report their body weights than male participants:
*Data of female participants are more likely missed not because of data (body weights) themselves but because female tend to be reluctant to report their body weights
*In other words, the variable of ''body weight'' itself does 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 does not depend on observed data nor on 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:
*Data after the move are missed not because of data (body weights) themselves nor because of the participant's unobserved (unmeasured) characteristic
|}
