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→Three mechanisms (assumptions) of data missing
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!Description
![*Example]<br>A cohort study in which participants self report their body weight every week to research center via special app installed on their smartphones for 52 weeks in total
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!Missing not at random<br>MNAR
!Missing at randam<br>MAR
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*Missing does not depend on '''(other) unobserved data''', but may depend on '''observed data'''
*The cause of missing can be explained by
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!Missing completely at random<br>MCAR
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*Missing does NOT depend on '''(other) observed datavalues''' NOR on '''unobserved data(missing) values'''*Missing occurs purely at random independely from any observed and unobserved datathemselves
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*A participant moves moved to outside cohort area because of family affair which has nothing to do with the study and is lost to follow up at after the 10th week:*A participant fails to report body weights because of malfunction of the app between the 15th and 17th weeks**Data after the move are missed not because The reasons (mechanisms) of data missing have nothing to do with other observed (body weightscertainly reported) values, values in other variables, nor unobserved (missing) values themselves**Missing mechanism is completely at random, i.e., nor because completely free from either of the participant's observed values or unobserved (unmeasuredmissing) characteristic related to the studyvalues
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