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16b. Accessing Data: Means in SAS ®

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1 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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16b. Accessing Data: Means in SAS ® 2 Prerequisites Recommended modules to complete before viewing this module (cont’d) NLTS2 Documentation 10. Overview 11. Data Dictionaries 12. Quick References Accessing Data 14b. Files in SAS 15b. Frequencies in SAS

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16b. Accessing Data: Means in SAS ® 3 Overview Purpose Exploring existing data Means Comparative means Weights Closing Important information

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16b. Accessing Data: Means in SAS ® 4 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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16b. Accessing Data: Means in SAS ® 5 Purpose Learn to Run simple statistical procedures Means Watch for Missing values n’s Weighted vs. unweighted data

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16b. Accessing Data: Means in SAS ® 6 Means How to run means Means are run on continuous variables such as Number of months Income Age Test scores Syntax with options to control printing PROC MEANS data = sasdb.n2w2dirassess mean min max n maxdec=2; /*limits output*/ VAR ndaAP_w ; run ; These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 7 Means These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 8 Means Important: Do not use the 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 stratified sample. More about this later. These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 9 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 error in statistics. Syntax: Simply add a CLASS statement. PROC MEANS data = sasdb.n2w2dirassess mean min max n maxdec=2 ; CLASS na_age4 ; VAR ndaAP_w ; These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 10 Comparative means These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 11 Means and comparative means: example Means and comparative means Use the Wave 3 parent/youth interview file. Run means on np3NbrProbs. Run comparative means on np3NbrProbs by W3_AgeHdr2005 and by W3_DisHdr2005. These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 12 Means and comparative means: Example These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 13 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 means and comparative means can be run with weights. The weighted means will be correct. The weighted standard errors will not be correct using these procedures; do not report them. Weighting in SAS requires a WEIGHT statement. The procedures themselves do not change. Weights are applied when there is a WEIGHT statement. These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 14 Weights Syntax PROC MEANS data = sasdb.n2w3ParYouth mean min max maxdec=2 ; WEIGHT np3Wt; VAR np3NbrProbs ; run ; To turn the weight off, omit the statement or comment it out. PROC MEANS data = sasdb.n2w3ParYouth mean min max maxdec=2 ; *WEIGHT np3Wt; VAR np3NbrProbs ; run ; These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 15 Weights: Example Weights: Run the 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 These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 16 Weights: Example These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 17 Weights: Example These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 18 Weighted example These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 19 Unweighted example These results cannot be replicated with full dataset; all output in modules generated with a random subset of the full data.

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16b. Accessing Data: Means in SAS ® 20 Closing Topics discussed in this module Exploring existing data Means Comparative means Weights Next module: 17b. Accessing Data: Manipulating Variables in SAS

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16b. Accessing Data: Means in SAS ® 21 Important information NLTS2 website contains reports, data tables, and other project-related information http://nlts2.org/http://nlts2.org/ Information about obtaining the NLTS2 database and documentation can be found on the NCES website http://nces.ed.gov/statprog/rudman/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.asphttp://nces.ed.gov/statprog/instruct.asp E-mail address: nlts2@sri.com

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