The SEQDESIGN Procedure
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Overview
- Getting Started
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Syntax
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Details
Fixed-Sample Clinical Trials One-Sided Fixed-Sample Tests in Clinical Trials Two-Sided Fixed-Sample Tests in Clinical Trials Group Sequential Methods Statistical Assumptions for Group Sequential Designs Boundary Scales Boundary Variables Type I and Type II Errors Unified Family Methods Haybittle-Peto Method Whitehead Methods Error Spending Methods Acceptance (beta) Boundary Boundary Adjustments for Overlapping Lower and Upper beta Boundaries Specified and Derived Parameters Applicable Boundary Keys Sample Size Computation Applicable One-Sample Tests and Sample Size Computation Applicable Two-Sample Tests and Sample Size Computation Applicable Regression Parameter Tests and Sample Size Computation Aspects of Group Sequential Designs Summary of Methods in Group Sequential Designs Table Output ODS Table Names Graphics Output ODS Graphics Acknowledgments
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Examples
Creating Fixed-Sample Designs Creating a One-Sided O’Brien-Fleming Design Creating Two-Sided Pocock and O’Brien-Fleming Designs Generating Graphics Display for Sequential Designs Creating Designs Using Haybittle-Peto Methods Creating Designs with Various Stopping Criteria Creating Whitehead’s Triangular Designs Creating a One-Sided Error Spending Design Creating Designs with Various Number of Stages Creating Two-Sided Error Spending Designs with and without Overlapping Lower and Upper beta Boundaries Creating a Two-Sided Asymmetric Error Spending Design with Early Stopping to Reject H0 Creating a Two-Sided Asymmetric Error Spending Design with Early Stopping to Reject or Accept H0
- References
Example 80.4 Generating Graphics Display for Sequential Designs
This example creates the same group sequential design as in Example 80.3 and creates graphics by using ODS Graphics. The following statements request all available graphs in the SEQDESIGN procedure:
ods graphics on;
proc seqdesign altref=0.4
plots=all
;
TwoSidedPocock: design nstages=4 method=poc;
TwoSidedOBrienFleming: design nstages=4 method=obf;
run;
ods graphics off;
With the PLOTS=ALL option, a detailed boundary plot with the rejection region and acceptance region is displayed for the Pocock design, as shown in Output 80.4.1. By default (or equivalently if you specify STOP=REJECT), the rejection boundaries are also generated at interim stages.
The plot shows identical boundary values in each boundary in the standardized 
scale for the Pocock design. The information level and critical value for the corresponding fixed-sample design are also displayed.
With the PLOTS=ALL option, a detailed boundary plot with the rejection region and acceptance region is also displayed for the O’Brien-Fleming design, as shown in Output 80.4.2. The plot shows that the rejection boundary values are decreasing as the trial advances in the standardized scale.
With the PLOTS=ALL option, the procedure displays a plot of average sample numbers (expected sample sizes for nonsurvival data or expected numbers of events for survival data) under various hypothetical references for all designs simultaneously, as shown in Output 80.4.3. By default, the option CREF= 
and expected sample sizes under the hypothetical references 
are displayed, where 
are values specified in the CREF= option. These CREF= values are displayed on the horizontal axis.
The plot shows that the Pocock design has a larger expected sample size than the O’Brien-Fleming design under the null hypothesis (
) and has a smaller expected sample size under the alternative hypothesis (
).
With the PLOTS=ALL option, the procedure displays a plot of the power curves under various hypothetical references for all designs simultaneously, as shown in Output 80.4.4. By default, the option CREF= and powers under hypothetical references are displayed, where are values specified in the CREF= option. These CREF= values are displayed on the horizontal axis.
Under the null hypothesis, , the power is 
, the upper Type I error probability. Under the alternative hypothesis, , the power is 
, one minus the Type II error probability. The plot shows only minor difference between the two designs.
With the PLOTS=ALL option, the procedure displays a plot of sequential boundaries for all designs simultaneously, as shown in Output 80.4.5. By default (or equivalently if you specify HSCALE=INFO in the COMBINEDBOUNDARY option), the information levels are used on the horizontal axis.
The plot shows that the 
boundary values (in absolute value) created from the O’Brien-Fleming method are greater in early stages and smaller in later stages than the boundary values from the Pocock method. The plot also shows that the information level in the Pocock design is larger than the corresponding level in the O’Brien-Fleming design at each stage.
With the PLOTS=ALL option, the procedure displays a plot of cumulative error spends for all boundaries in the designs simultaneously, as shown in Output 80.4.6. With a symmetric two-sided design, cumulative error spending is displayed only for the upper boundary. The plot shows that for the upper boundary, the O’Brien-Fleming method spends fewer errors in early stages and more errors in later stages than the corresponding Pocock method.
