Desktop Survival Guide
by Graham Williams
The simplest of imputations involves replacing all missing values for a variable with a single value! This makes most sense when we know that the missing values actually indicate that the value is 0 rather than unknown. For example, in a taxation context, if a tax payer does not provide a value for a specific type of deduction, then we might assume that they intend it to be zero. Similarly, if the number of children in a family is not recorded, it could be a reasonable assumption to assume it is zero.
For categoric data the simplest approach to imputation is to replace missing values with a special value, Missing.