Table 1 Patterns of missing data
Missing data pattern | Description |
|---|---|
Missing completely at random (MCAR) | • Data are missing for reasons not related to observed or unobserved variables • Simple statistical approaches to deal with missing data can provide unbiased results |
Missing at random (MAR) | • Probability of missingness is related to observed data but not to unobserved data • MAR is the assumption for most imputation methods |
Missing not at random (MNAR) | • Missingness is related to unobserved data |