10. nlts2 documentation overview

10. NLTS2 Documentation Overview

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Prerequisites• Recommended modules to complete before viewing this

module 1. Introduction to the NLTS2 Training Modules 2. NLTS2 Study Overview 3. NLTS2 Study Design and Sampling NLTS2 Data Sources, either:

• 4. Parent and Youth Surveys or • 5. School Surveys, Student Assessments, and Transcripts

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Overview NLTS2 documentation overview What is included in the documentation Table of contents Database overview document Database structures document Index of variables Other resources/documents in the documentation Data collection instruments File documentation Closing Important information

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NLTS2 documentation overview

• NLTS2 documentation includes the information necessary for learning about the NLTS2 study, the sources of data, and the database.

• Data documentation is by data source and by wave.

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What is included in the documentation• HTML table of contents• Database overview document• Database structures document• Data dictionaries• File documentation• Data collection instruments• Index of variables• SPSS user notes• Quick references

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What is included in the documentation• One data file for each data source in a wave in both SAS® and

SPSS® formats• SAS version

SAS format library SAS programming code for creating user defined formats SAS PROC Contents output for each file lists variable name,

variable label, and associated value format.• SPSS version

SPSS users’ notes Variable names, variable labels, missing values ranges, and

value labels can be viewed by opening file in the SPSS “Variable View” data window.

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Table of contents• HTML table of contents

Documents are accessed via hyperlinks in an HTML table of contents.

The contents has 2 levels; the top level links to either• A document that pertains to all waves, such as the overview,

index of variables, or quick reference guide.• A secondary table of contents by data collection wave listing

data dictionaries, instruments, and file documentation within that wave.

To use a hyperlink, click on any blue underlined text to be taken directly to a document or detailed table of contents by Wave.

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Table of contents

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Database overview document• Provides general and background information about the

study.• Addresses sampling, data collection, weighting,

response rates, and other important concerns in using these data. Describes each data collection effort by wave. Discusses weighting and calculating weighted standard

errors. Includes a table of response rates for each instrument by

wave.• Explains disability categorizations and defines the

disability categories.

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Database structures document• Database structures document contains general

information about the database. • Lists all files resulting from data collection for each wave.

Indexed by a letter for wave and number for instrument.• For each file, information includes file name, variable

prefix, main weight, number of records, and how file is linked to other files. All NLTS2 files link by a single identifier or key variable “ID.” Unit of analysis for all files is an individual youth within a

wave and data collection instrument. Every record in a file represents a youth in the sample for

whom there is data for that source.

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Database structures document• The database structures also includes

Information about the sample data for calculating weighted standard errors.

Counts of cases that appear in multiple files.• For example, the number of cases that have data in the Wave 1

Parent Survey file, School Program Survey file, and Teacher Survey file, or any combination of these.

Information about value formats and value labels. Sources of data for each file.

• For example: Parent/Youth Survey, Teacher Survey, School Program Survey, Direct Assessment, etc.

Naming conventions for variables within each file.

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Database structures document• Naming conventions

Each file name and variable name reflects the study, wave, and data source.• “N2W2Tchr” is [n2] NLTS2 study [W2] Wave 2 [Tchr] Teacher

Survey.• “N2W1Prog” is [n2] NLTS2 study [W1] Wave 1 [Prog] School

Program Survey. Prefix of variables within a file indicates the study,

wave, and source; if applicable names also refer to a specific section and question number in the source instrument.• “np1G4e” is [n] NLTS2 study, [p] Parent/guardian interview, [1]

Wave 1, [G] Section G, [4e] Question 4e.

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Index of variables• The index is a single document that lists every variable in

the database alphabetically.• Variables are indexed to the data dictionaries.• Page numbers match the data dictionary section indexed

in the table of contents. When there are sections in a data collection instrument, the

pages are numbered within the section. Example: nts2C8 is indexed to B4-C-2

• “B4” refers to the Wave and instrument tag in the table of contents [Wave 2, fourth instrument listed], “C” indicates it is from section C within the instrument, and “2” that it is on page 2 of the data dictionary within that section.

• Note: In the index tags, “A” is Wave 1, “B” is Wave 2, “C” is Wave 3, etc.

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Index of variables: Example

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Other documents• Notes to SPSS users

Notes specific to using SPSS files converted from SAS, such as missing values and value labels created from SAS formats library.

• Quick references Useful information for using these data. Discussed in a separate module.

• Data dictionaries Variable-by-variable description. Discussed in in a separate module.

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Data collection instruments• All data collection instruments from a given wave

are included.• In some instances, instruments for a data

collection effort are in multiple formats. Example: NLTS2 Parent Interview and Family Mail

Survey questionnaire. Data from multiple formats are usually blended into a

single file.• There is one file for each data collection effort whether multiple

forms or a single form were used to collect the data.

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File documentation• One file document for every file in the database.

Files are by wave and by data source within wave.• File documentation lists the variables in each file

alphabetically.• A procedure in SAS (PROC Contents) produces the

listing.• For each variable, the contents list

Name (same in both SAS and SPSS). Variable label (same in both SAS and SPSS). Associated value formats (stored differently in SAS and

SPSS).

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File documentation• Associated value formats

An associated format replaces number values with value descriptions in printed output.

Example: With the format “ynfmt”, “(0) no” and “(1) yes” are listed in output instead of just the numbers “0” and “1.”

In SAS, formats are in an externally stored format library.• A program for recompiling the SAS formats library is included with

the documentation. In SPSS, the value formats are stored with each individual

variable.

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File documentation: Example

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Closing• Topics discussed in this module

NLTS2 documentation overview What is included in the documentation Linked table of contents Database overview document Database structures document Index of variables Other resources/documents in the documentation Data collection instruments File documentation

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Closing• Next module:

11. NLTS2 Documentation: Data Dictionaries

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Important information NLTS2 website contains reports, data tables, and

other project-related information http://nlts2.org/

Information about obtaining the NLTS2 database and documentation can be found on the NCES website http://nces.ed.gov/statprog/rudman/

General information about restricted data licenses can be found on the NCES website http://nces.ed.gov/statprog/instruct.asp

E-mail address: [email protected]

http://nlts2.org/

http://nces.ed.gov/statprog/rudman/

http://nces.ed.gov/statprog/instruct.asp