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16a. Accessing Data: Means in SSPS ® 2 Prerequisites Recommended modules to complete before viewing this module (cont’d) NLTS2 Documentation 10. Overview 11. Data Dictionaries 12. Quick References Accessing Data 14a. Files in SPSS 15a. Frequencies in SPSS
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16a. Accessing Data: Means in SPSS®
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16a. Accessing Data: Means in SSPS®
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
9. Weighting and Weighted Standard Errors
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16a. Accessing Data: Means in SSPS®
Prerequisites• Recommended modules to complete before viewing
this module (cont’d) NLTS2 Documentation
• 10. Overview• 11. Data Dictionaries• 12. Quick References
Accessing Data• 14a. Files in SPSS• 15a. Frequencies in SPSS
16a. Accessing Data: Means in SSPS®
Overview Purpose Exploring existing data
• Means• Comparative means
Weights Closing Important information
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16a. Accessing Data: Means in SSPS®
NLTS2 restricted-use data• NLTS2 data are restricted.• Data used in these presentations are from a
randomly selected subset of the restricted-use NLTS2 data.
• Results in these presentations cannot be replicated with the NLTS2 data licensed by NCES.
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16a. Accessing Data: Means in SSPS®
Purpose• Learn to
Run simple statistical procedures• Means• Comparative means
Watch for• Missing values• n’s• Weighted vs. unweighted data
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16a. Accessing Data: Means in SSPS®
Means• How to run means• Means are run on continuous variables such as
Number of months Income Age Test scores.
• SyntaxDESCRIPTIVES VARIABLES=ndaAP_w /STATISTICS=MEAN MIN MAX.
7These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Means• From menu
Analyze: Descriptive Statistics: Descriptives Select options and uncheck “Std Deviation” in pop-up box.
• Important: Although they print by default, do not use standard deviations (or optional standard errors) from this procedure. These data are from a stratified sample, so standard errors are not
calculated correctly in this procedure. Standard errors in this procedure assume a simple random sample,
not a complex sample.• More about this later.
8These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Means
9These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Comparative means• As with frequencies, comparative means can be run in a single
step.• The by- (or independent) variable must be categorical.• Reminder: Do not include the standard deviation in statistics.• Syntax
MEANS TABLES=ndaAP_w BY na_age4 /CELLS MEAN COUNT.
10These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Comparative means• From menu
Analyze: Compare Means: Means Locate [means variable name] in the variable list and click the right-facing
arrow to the left of the “Dependent List” box to select it.• Means variable
Locate [comparative variable name] in the list and click the right-facing arrow next to the “Independent” box.
• By-variable Click on “Options” and under “Cell Statistics” select “Standard Deviation.” Click the left-facing arrow. Click Continue. Press “OK” to run or select “Paste” to run code from syntax editor.
11These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Comparative means
12These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Means and comparative means: Example• Means and comparative means
Open the Wave 3 parent/youth interview file. Run means on np3NbrProbs. Run comparative means on np3NbrProbs by
W3_AgeHdr2005 and by W3_DisHdr2005. Important: If you use the “Paste” option, you will
be able to use this code again.
13These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Means and comparative means: Example
14These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Means and comparative means: Example
15These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Means and comparative means: Example
16These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Weights• How to weight data.• Running procedures unweighted is useful for exploratory analysis and
recommended for becoming familiar with the data. It is important to review the unweighted n’s
• However, unweighted results must never be reported.• The procedures we used to calculate frequencies, means, crosstabs, and
comparative means can be run with weights. The weighted means or percentages will be correct. The weighted standard errors will not be correct using these procedures; do
not report them.• Weighting in SPSS is a toggle.
The weight option can be turned on and off. The procedures themselves do not change.
• Weights are applied when the weight toggle is on.• Weights are not applied when the weight toggle is off.
17These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Weights• Syntax: weight on
WEIGHT BY wt_npr1.
• Syntax: weight offWEIGHT OFF.
• Menu: weight on Select “Weight Cases” from “Data” menu. Click the “Weight Cases By” radio button. Locate [weight variable] in the list of variables. Click the right-facing arrow to select the weight. Press “OK” to run or select “Paste” to run code from syntax editor.
• Menu: weight off Select “Weight Cases” from “Data” menu. Click the “Do Not Weight Cases” radio button. Press “OK” to run or select “Paste” to run code from syntax editor.
18These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Weights: Example• Weights: Run earlier examples with a weight.
Run means example weighted with np3Wt.• W3 parent interview weight np3wt• np3NbrProbs• np3NbrProbs by W3_AgeHdr2005 and by
W3_DisHdr2005 Turn weight off.
19These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Weights: Example
20These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Weights: Example
21These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Weights: Example
22These results cannot be replicated with full dataset; all outputin modules generated with a random subset of the full data.
16a. Accessing Data: Means in SSPS®
Closing• Topics discussed in this module
Exploring existing data• Means• Comparative means
Weights• Next module
17a. Accessing Data: Manipulating Variables in SPSS
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16a. Accessing Data: Means in SSPS®
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]
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