Imputation is a way of inferring missing values in a test result. Basically, an educated guess. It is used mostly in Genome-Wide Association Studies (GWAS) based on low coverage sequencing. It is also used in genetic genealogy matching segment sites when dissimilar microarrays are used and need to be compared. When studying larger populations and trends, it is an effective technique. But, to date, it is inaccurate for individual testers trying to determine particular missing values. Segment Matching Sites utilizing the technique will often return much larger matching segment lengths than would otherwise be measured.