Week three Flashcards
What is the difference between missing data patterns and missing data mechanisms?
Missing data pattern describes where the data are missing within a dataset.
Missing data mechanism describes why the data may be missing, especially in that pattern. However, it does not provide a causal relationship, instead it refers to a mathematical relationship between the missing data and the variable.
What are missing at random (MAR) data?
There is no relationship between the values missing and the values of the variable. It does, however, refer to the relationship that exists between missing data of one variable and the values of another variable.
What is Missing Completely At Random data (MCAR)?
When there is no relationship between variables and missing data.
It assumes that missingness is completely unrelated to data.
What are Missing Not At Random (MNAR) data?
The value of the missing data for a variable is related to that variable.
Rubin defines missing data as a variable, called R. R has a probabilty distribution. The probability of missing data may or may not be related to the other variables in the dataset.
What differentiates the missing data mechanism?
The relationship between R and the data.
Which missing data mechanism is known as “ignorable missingness”?
MAR
What are some reasons for missing data?
Participants drop out of study.
Technical issues.
Subset of population may not sign up for study.
Cut-off criteria may exclude people from your population of interest.
Unobserved variables that systematically bias participation.
Which mechanism of missing data is assumed in most stat test?
MCAR
MAR?
Missing data can be explained by another variable, but not the variable of the data.
MNAR?
The missing data have a relationship to the variable of the data, but not the other variables.
How do we determine whether data is MCAR or MAR?
We create a variable, with values of 0 or 1, that correspond to whether data is present or not. A missingness variable.
We then do a t-test on the
