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Simulating the Performance of Estimators of the Number of Duplicates in a Database

In: Computing Science and Statistics

Author

Listed:
  • John C. Handley

    (OCLC Online Computer Library Center, Office of Research)

  • John A. Bunge

    (Cornell University, Department of Economic and Social Statistics)

Abstract

A large database consisting of N records is partitioned into K equivalence classes, which are sets of duplicate records. It is desired to estimate K, the number of unique records, based on a small sampling fraction of either individual records or complete equivalence classes. There exists a unique unbiased estimator based on a simple random sample of individual records, and an asymptotically unbiased estimator exists when the sample consists of complete classes drawn without replacement. In both cases, the variance of the estimators must be obtained through simulation. A UNIX software system was written to explore the variance of these estimators for large database-type populations with many singletons. The software system consists of population generators, an efficient sampling program, and programs to compute estimators. Simulation results for both estimators are presented which show that the variance of the unbiased estimator based on sampling individuals is too great to be useful for small sampling fractions but that good estimates can be obtained sampling by class.

Suggested Citation

  • John C. Handley & John A. Bunge, 1992. "Simulating the Performance of Estimators of the Number of Duplicates in a Database," Springer Books, in: Connie Page & Raoul LePage (ed.), Computing Science and Statistics, pages 366-369, Springer.
    • Handle: RePEc:spr:sprchp:978-1-4612-2856-1_55
    DOI: 10.1007/978-1-4612-2856-1_55
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