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Missing boundary using Proc SEQDESIGN

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JCJ
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Missing boundary using Proc SEQDESIGN

Hi all,

Has anyone used Proc SEQDESIGN to calculate the boundary values of a sequential group design using O'Brien Fleming type error spending function? I tried the following codes using 11 stages but the boundary values are missing for the first stage. I think this is caused by the information proportion less than 0.1 because when I tried nstage=10 or 12, the procedure produced +/-6.99 and missing values, respectively, for the first stage. The corresponding information proportion is 0.1 and 0.0833, respectively.

codes:

proc seqdesign ;

  TwoSidedOBF: design nstages=11 method=errfuncobf ;

run;

The resulting boundary table:

Boundary Information (Standardized Z Scale)
Null Reference = 0
_Stage_InformationAlternativeBoundary Values
LevelReferenceLowerUpper
ProportionLowerUpperAlphaAlpha
10.0909-0.99520.9952..
20.1818-1.407421.40742-5.127545.12754
30.2727-1.723731.72373-4.136444.13644
40.3636-1.99041.9904-3.545893.54589
50.4545-2.225332.22533-3.148653.14865
60.5455-2.437732.43773-2.859732.85973
70.6364-2.633052.63305-2.637842.63784
80.7273-2.814852.81485-2.460622.46062
90.8182-2.985592.98559-2.314932.31493
100.9091-3.147093.14709-2.19242.1924
111-3.30073.3007-2.087462.08746

The problem only appear when I use 'errfuncobf' (for example, 'obf' and 'errfuncpoc' are both fine and can produce complete boundary values for any stage). Is there any solution to solve this problem and let the procedure produce the value for the first stage?

I am using SAS v9.3.

Thank you.

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