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st: Creating missing data

From   [email protected]
To   [email protected]
Subject   st: Creating missing data
Date   Wed, 03 Nov 2004 20:01:14 -0500

I am working on a very large data set that has a left-truncation problem - specifically, incorrect founding dates for a fair number of firms, meaning that I cannot really determine the age of these particular firms. In attempt to address this problem, I am exploring the possibility of dropping the incorrect dates and using multiple imputation procedures to estimate new dates. Because of confidentiality constraints associated with the use of the aforementioned data set, I am limited to testing possible solutions to this problem using a surrogate but structural similar data set. My question is about making an adjustment to the surrogate data set. The surrogate data set contains about 3500 cases, some of which have just one record per case, and others have multiple records. Each record has a variable recording an entering time and an exit time for that record. Hence, single record cases have one entry time and one exit time; multiple record cases have multiple entry and multiple exit times. I would like to convert the first entry time for every fifth multiple-record case in this data set into a missing value. Are there any suggestions for how this might be done. Thanks. *
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