CODES 2000 User Forum -- Data Network Note #2
Multiple Imputation and One-to-One Links
Applies to: CODES 2000 Version 2.1.314.
Last updated: Monday November 12, 2001.
SUMMARY
The first step for multiple imputation of linked record pairs is to run and merge several match passes in CODES 2000 at a very low cutoff probability, say 0.001. This produces a Match Pairs In Sets table that contains all record pairs with match probabilities greater than 0.001. The Match Pairs In Sets table approximates the posterior distribution of match probabilities for all record pairs given observed agreements and disagreements. You can impute multiple complete sets of linked pairs by simulating draws from this distribution. Because of the low cutoff, the tabulated links are usually not a one-to-one match. That is, one Crash record may be linked to more than one Inpatient record or more than one Crash record may be linked to the same Inpatient record. The many-to-many match must be reduced to a one-to-one match before you can analyze the imputed linked pairs.
CODES 2000 Version 2.1.314 does not include the queries needed to simulate draws from the posterior distribution or to select one-to-one matches from the Match Pairs In Sets table. You can write your own queries in Access to do these tasks, or you can import the necessary queries into any match database as a new form. This note describes how to import the new form and use it to impute complete sets of linked pairs and produce a final one-to-one match.
PROCEDURE
- Download the new form.
The new form is available in an Access 2000 database that you can download from this site. Download ImputeForm.mdb database now (120 KB).
- Run and merge all match passes.
The first step for multiple imputation of linked record pairs is to run and merge several match passes in CODES 2000 at a very low cutoff probability, say 0.001.
- Import the new form.
Open the CODES 2000 link database in your project folder, say CrashHospital2.mdb.
Select Forms in the database window. Right click on the unused area and select Import... Navigate to the ImputeForm.mdb database and import frmImpute.
Open the Visual Basic environment by typing CTRL+G. Select Tools on the menu bar and click on References. If the CODES2000Lib.mde library database is not listed as an available reference, browse to the CODES2000\Library folder and add it:
Close the Visual Basic environment by typing ALT+Q.
- Open and use the new form and impute multiple complete links.
Select Forms in the database window and double-click on the name of the new form, frmImpute:
Enter the number of records in Table A (Crash), say 56689.
Enter the number of records in Table B (Hospital), say 12877.
Enter your estimate of the total number of true matched record pairs for Table A and Table B, say 1200.
Select the imputation option. Normally this will be Impute missing links.
Select the number of imputations. Normally this will be 5.
Click on Run. CODES 2000 will read your Match Pairs In Sets table and impute multiple complete sets of one-to-one linked pairs in tables named LinkedPairs1, LinkedPairs2, ...
