If each observation in the data set provides one unit of information in a hypothesis testing (such as a onesample test for the mean), the SAMPLESIZE statement computes the required sample sizes for each sequential design that is specified in a DESIGN statement. However, for a survival analysis, an individual in the survival time data might provide only partial information because of censoring. For this hypothesis, the SAMPLESIZE statement computes the required numbers of events. With additional accrual information in a survival analysis, the sample sizes can also be computed.
Only one SAMPLESIZE statement can be specified. For each specified group sequential design, the SAMPLESIZE statement computes the required sample sizes or numbers of events. The SAMPLESIZE statement is not required if the SEQDESIGN procedure is used only to compare features among different designs.
You can specify the following option:
Table 89.4 summarizes the types of modelrequest that you can specify.
Table 89.4: MODEL= Option
Option 
Description 

FixedSample Models 

Specifies the sample size for a fixedsample design 

Specifies the number of events for a fixedsample design 

OneSample Models 

Specifies the onesample Z test for the mean 

Specifies the onesample test for the binomial proportion 

TwoSample Models 

Specifies the twosample Z test for the mean difference 

Specifies the twosample test for binomial proportions 

Specifies the logrank test for two survival distributions 

Regression Models 

Specifies the test for a regression parameter 

Specifies the test for a logistic regression parameter 

Specifies the test for a proportional hazards regression parameter 
The MODEL=INPUTNOBS option specifies the input sample size from a fixedsample study of nonsurvival data, and the MODEL=INPUTNEVENTS option specifies the number of events from a fixedsample study of survival data. The remaining MODEL= options specify the statistical models that are used to compute the required sample size. The default is MODEL=TWOSAMPLEMEAN, the twosample Z test for the mean difference.
When MODEL=INPUTNOBS or MODEL=INPUTNEVENTS, the required sample size or number of events for the group sequential trial is computed by multiplying the input sample size or number of events by the ratio of the design information level to its corresponding fixedsample information level. This ratio can be obtained by dividing the Max Information (Percent FixedSample) in the "Design Information" table by 100. For a description of the "Design Information" table, see the section Design Information.
The following two options compute the required sample size or number of events for a group sequential trial by using the sample size or number of events for the fixedsample design:
The following two options compute the required sample size for a onesample group sequential test:
The following three options compute the required sample size or number of events for a twosample group sequential trial.