Summary of survey software: SUDAAN

Vendor

Research Triangle Institute

Types of designs that can be accommodated.

Multiple design options allow users to analyze data from stratified, cluster sample, or multistage sample designs. Sample members may have been selected with unequal probabilities, and either with or without replacement. Any number of strata and stages can be specified. In addition, different design options may be combined in one study if different sampling methods were used for parts of the population.

Types of estimands and statistical analyses that can be accommodated.

SUDAAN includes the following statistical procedures:

• MULTILOG: Fits multinomial logistic regression models to ordinal and nominal categorical data and computes hypothesis tests for model parameters. Estimates odds ratios and their 95% confidence intervals for each model parameter. Has GEE (Generalized Estimating Equation) modeling capabilities for efficient parameter estimation.
• REGRESS: Fits linear regression models to continuous outcomes and performs hypothesis tests concerning the model parameters.
• LOGISTIC: Fits logistic regression models to binary data and computes hypothesis tests for model parameters. Estimates odds ratios and their 95% confidence intervals for each model parameter.
• SURVIVAL: Fits proportional hazards (Cox regression) models to failure time data. Estimates hazard ratios and their 95% confidence intervals for each model parameter.
• CROSSTAB: Computes frequencies, percentage distributions, odds ratios, relative risks, and their standard errors (or confidence intervals) for user-specified cross-tabulations, as well as chi-square tests of independence and the Cochran-Mantel-Haenszel chi-square test for stratified two-way tables.
• DESCRIPT: Computes estimates of means, totals, proportions, percentages, geometric means, quantiles, and their standard errors. Also computes standardized estimates and tests of single degree-of-freedom contrasts among levels of a categorical variable.
• RATIO: Computes estimates and standard errors of generalized ratios of the form (Summation y) / (Summation x), where x and y are observed variables. Also computes standardized estimates and tests single-degree-of-freedom contrasts among levels of a categorical variable.
• The EFFECT statement allows users to specify contrasts of regression coefficients and hypothesis tests using simple effect names.

Restrictions on number of variables or observations.

None

Primary methods used for variance estimation.

The Taylor series linearization method (GEE for regression models) is used combined with variance estimation formulas specific to the sample design. The user does not need to develop special replicate weights since the sample design can be specified directly to the program.

Jackknife and Balanced Repeated Replication (BRR) variance estimation is also supported.

General description of the "feel" of the software.

SUDAAN uses a SAS-like language. There are two versions of Sudaan with different data interfaces:

• "SAS-callable" Sudaan: SUDAAN is called directly as a SAS procedure.
• "Standalone Sudaan": Independent program that reads external file formats, including SAS files or SPSS files.

In either case, the same programming language is used.

Platforms on which the software can be run.

• PCs under Windows 95 or later versions. This is now the primary platform for Sudaan.
• Sun SPARC computers under Solaris 2.6 and up.

SUDAAN is distributed as a precompiled program.

Availability, pricing and terms.

Release 8.0 of Sudaan is the current version (see list of enhanced features ).

SUDAAN is available under annual site licenses. Annual academic site license renewal prices range from $60 to $385 per user (depending on volume), with new licenses costing about twice as much. Government and commercial annual site license prices range from $65 to $735 per user depending on product and volume See pricing details at Sudaan Web site.

Contact information.

SUDAAN Product Coordinator
Research Triangle Institute
3040 Cornwallis Road
Research Triangle Park NC 27709-2194
Telephone: 919-541-6602
FAX: 919-541-7431
Email: SUDAAN@rti.org
URL: http://www.rti.org/sudaan/

Additional information.

SUDAAN offers public 2-day or 3-day training classes several times each year. Classes can also be taught at user sites.

The following papers about Sudaan are available on-line:

• Full help manual may be viewed on-line.
• Bieler and Williams (1996), "Application of the SUDAAN Software Package to Clustered Data Problems: Pharmaceutical Research."
• "Analyzing Repeated Measures and Cluster-Correlated Data Using SUDAAN Release 7.5" (1997).
• "Analyzing Survey Data Using SUDAAN Release 7.5" (1997, compares Taylor series, jackknife and BRR variance estimates)