差分

!rowspan="2"|[Example]<br>A cohort study in which participants self report their body weight every week via special app installed on their smartphones for 52 weeks in total. Demographic variables are also collected.

*Some participants '''intentionally deny denied to report higher body weights they dondidn't like''' and only report reported lower body weights they likeaccepted*Researchers have no information why they denied to report body weights in several weeks**Data of those participants are missed '''Missing occurred because of the values in the variable ''body weight'' themselves'''**Researchers cannot explain/predict the missing mechanism by from other observed (reported) body weights or other variables

*15% of female participants denied to report their body weights after the agreement participation regardless of measured body weights, but only 1% of male denied to report:*Researchers can identify that female participants more likely denied to report body weights than male**Unobserved (missing, unrepoted) values in the variable ''Missing occurred not because of body weight'' weights themselves did not affect the missing, but because of another variable ''sex'' can explain the reason of missing**Missing mechanism is at random, i.e., free from unobserved (missing) values , but it's applicable only inside each participant**Missing mechanism is NOT at random, i.e., NOT free from another variable ''sex''; missing occurred depending on the values in the variable ''sex''

*A participant moved to outside cohort area because of family affair which has nothing to do with the study and is was lost to follow up after the 10th week*A participant fails failed to report body weights because of malfunction of the app between the 15th and 17th weeks**The reasons (mechanisms) Missing occurred not because of missing have nothing to do with other observed (certainly reported) values, values in body weights themselves nor other variables, nor unobserved (missing) values themselves**Missing mechanism is completely at random, i.e., completely free from either both of missing (unobserved) values and observed values in body weight or unobserved (missing) valuesin other variables