Missing Data

Question 1

Typology of missingness mechanisms

Answer 1

Missing completely at random
Missing at random
Missing not at random

Question 2

MCAR implies

Answer 2

• missingness is not related to the observed and missing data
• no bias due to systematic differences
• responders are representative sample of the population -> only loss of power

Question 3

MAR implies

Answer 3

• missingness may be related to the observed data but not the missing data
• no bias due to systematic differences given observed data
• subgroups of responders are representative sub samples of the population
• non response can be predicted by the observed data

Question 4

MNAR implies

Answer 4

• missingness are related to the missing data

- systematic bias due to systematic differences

Question 5

Typology when data is partially missing

Answer 5

• missing by design: not applicable items, incomplete designs
• partial non response: drop out,break of during interview
• item non response: skipped items, information lost