Using SAMHDA
- Overview
- Terms, formats, and statistical vocabulary
- Searching and finding the data you need
- Accessing data
- Downloading data
- Analyzing data using statistical software
- Online data analysis using SDA
- Producing Quick Tables
- More information
Online data analysis using SDA
In order to make its data holdings usable for a wider audience, SAMHDA has adopted a user-friendly online data analysis system, Survey Documentation and Analysis (SDA). Many SAMHDA data collections are available for online data analysis. This means that users can explore the data using certain statistical procedures without downloading data files and setup files, and without being familiar with any statistical package. SDA also offers a very useful option for those familiar with a statistical package: Users can create custom subsets of cases and/or variables and download the subsets to their computers. This option is attractive when the data file is very large, but only a few variables for a certain age, sex, or other subgroup are of interest.
SDA was developed and is maintained by the Computer-assisted Survey Methods Program (CSM) at the University of California, Berkeley.
The SDA Tutorial is an excellent resource that takes you on a guided interactive tour of some of the most commonly used features of SDA. Another useful resource is CSM's Online Help Files for SDA Users. Also, many of the analytical terms and options within SDA have clickable links that produce online help documentation.
SAMHDA currently uses SDA Version 3.1 for all studies formatted for this analysis package. Version 3.1 enables users to:
- Browse the SDA codebook
- Perform statistical procedures, such as:
- List values of individual cases
- Frequencies
- Crosstabulations
- Comparisons of means
- Correlation matrix
- Comparison of correlations
- Multiple regression
- Logit/probit regression
- Create bar, line, and pie charts for frequencies and crosstabulations
- Manipulate variables
- Recode variables
- Compute new variables
- List newly created variables
- Create customized subsets of selected variables and cases
- Download the subset, including:
- ASCII data file with optional delimiters
- SAS, SPSS, or Stata setup files
- Codebook customized for the selected subset
For SAMHDA studies available on SDA, there are several ways to access SDA: click on the Online Analysis link that appears on the search results page, select the Analyze and Subset tab that appears at the top of the Description page, or browse a list of data collections available for online analysis.
Note regarding studies with complex sample designs
Some of the studies archived by SAMHDA used a complex sample design. For these studies, great care should be taken when evaluating the results of analyses run on SDA. This is because only some statistical output correctly takes into account the complex sample design of the study. We are working to improve future versions of SDA so all available analysis features and statistical output will correctly account for studies with a complex design. Please refer to the online documentation for the most recent information on which SDA analytic features and statistical output correctly account for complex design. To determine whether a study used a complex sample design, refer to the codebook for that study.
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