abstract:In statistical analysis, data-values in a data set are missing completely at random (MCAR) if the events that lead to any particular data-item being missing are independent both of observable variables and of unobservable parameters of interest, and occur entirely at random. When data are MCAR, the analyses performed on the data are unbiased; however, data are rarely MCAR.
It isveryimportant to divide the missingdatainto three manners: missing at random (MAR), missingnotat random (MNAR) andmissing completelyat random (MCAR).