Editing Imputation (statistics) (section)

===Hot-deck===
A once-common method of imputation was hot-deck imputation where a missing value was imputed from a randomly selected similar record. The term "hot deck" dates back to the storage of data on [[punched card]]s, and indicates that the information donors come from the same dataset as the recipients. The stack of cards was "hot" because it was currently being processed.

One form of hot-deck imputation is called "last observation carried forward" (or LOCF for short), which involves sorting a dataset according to any of a number of variables, thus creating an ordered dataset. The technique then finds the first missing value and uses the cell value immediately prior to the data that are missing to impute the missing value. The process is repeated for the next cell with a missing value until all missing values have been imputed. In the common scenario in which the cases are repeated measurements of a variable for a person or other entity, this represents the belief that if a measurement is missing, the best guess is that it hasn't changed from the last time it was measured. This method is known to increase risk of increasing bias and potentially false conclusions. For this reason LOCF is not recommended for use.<ref>{{Cite journal|last1=Molnar|first1=Frank J.|last2=Hutton|first2=Brian|last3=Fergusson|first3=Dean|date=2008-10-07|title=Does analysis using "last observation carried forward" introduce bias in dementia research?|journal=Canadian Medical Association Journal|volume=179|issue=8|pages=751–753|doi=10.1503/cmaj.080820|issn=0820-3946|pmc=2553855|pmid=18838445}}</ref>