The NLMS Reference Manual is the key document describing the variables and subject matter content of the study. The manual is a documentation of the variables available for analysis, as they exist on the NLMS Extract and Analysis file systems. Variables were selected for inclusion in the Extract and Analysis file systems according to the most current research interests of NLMS Principal Investigators who are responsible for promoting the research interests of the NLMS sponsoring agencies.
Extract files consist of fixed format ASCII records which are documented completely in the NLMS Reference Manual. The content of an Extract file is intended to be a direct copy of the source master file variable for each cohort in the study. Since the definition of a variable may change over the longitudinal life of the NLMS follow-up period, Extract file records may contain a number of different codings for a given variable.
Analysis files are SAS datasets containing the final analytical version of each variable for the cohort. In the conversion of the variables from the Extract file version to the Analysis file version, the final standardization of the variables used was the one accommodating the greatest analytical potential across the cohorts of the study. Edits made and final analytical versions of the variables derived are describedin the Reference Manual Appendix.
Key Features of the Reference Manual:
The Reference Manual Title Page:
Variables are listed as an index.
Official variable reference name is given for each variable.
Reference page numbers are given for each variable.
Double-clicking on variable name takes cursor directly to start of
the variable description.
Variable description includes:
Official name of the variable.
Edit status in creation of Analysis variable from Extract variable.
Valid codes for variable as given on Extract file.
List of files for which variable does not exist.
Frequency count of valid variable values for each cohort.
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