The purpose of the SEQTEST procedure is to perform interim analyses for group sequential clinical trials. A group sequential trial provides for interim analyses before the formal completion of the trial while maintaining the specified overall Type I and Type II error probability levels.
You then use the SEQTEST procedure to compare the test statistic with the corresponding boundary values obtained with the SEQDESIGN procedure.
If the information levels do not match the information levels specified in the design, the SEQTEST procedure modifies the boundary values to adjust for new information levels.
At the end of a trial, the parameter estimate is computed. The median unbiased estimate, confidence limits, and pvalue depend on the specified sample space ordering. A sample space ordering specifies the ordering for test statistics resulting in the stopping of a trial. That is, for all the statistics in the rejection region and in acceptance region, the SEQTEST procedure provides three different sample space orderings: the stagewise ordering uses counterclockwise ordering around the continuous region, the LR ordering uses the distance between the observed Z statistic, z, and its hypothetical value, and the MLE ordering uses the observed maximum likelihood estimate.
Note that for some clinical trials, the information levels are derived from statistics based on individuals specified in the design plan and might not reach the target information levels. Thus, instead of specifying the number of individuals in the protocol, the information levels can be specified. You can then adjust the sample sizes to achieve the information levels for the trial.


For further details see the SAS/STAT User's Guide:
The SEQTEST Procedure
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