## Abstract

We consider a two-arm sequential trial with two or more strata. The

trial is monitored and terminated under the assumption of a common

treatment effect (if any) in all strata. A secondary question at the end of

the trial is: Does the treatment effect differ across strata—that is, is there

a treatment X stratum interaction? We provide a test of the null hypothesis

of no interaction—a test that recognizes the sequential stopping rule and

allows for uneven accumulation of information in the various strata, a

common case. In the case of two strata, and either a group-sequential

design or a fully-sequential linear-boundary design, an optimal property

of the test is derived. A computational algorithm is provided, and two

examples summarized.

trial is monitored and terminated under the assumption of a common

treatment effect (if any) in all strata. A secondary question at the end of

the trial is: Does the treatment effect differ across strata—that is, is there

a treatment X stratum interaction? We provide a test of the null hypothesis

of no interaction—a test that recognizes the sequential stopping rule and

allows for uneven accumulation of information in the various strata, a

common case. In the case of two strata, and either a group-sequential

design or a fully-sequential linear-boundary design, an optimal property

of the test is derived. A computational algorithm is provided, and two

examples summarized.

Original language | American English |
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Title of host publication | Institute of Mathematical Statistics Lecture Notes - Monograph Series |

Editors | John E. Kolassa, David Oakes |

Publisher | Institute of Mathematical Statistics |

Pages | 1-12 |

Number of pages | 12 |

ISBN (Print) | 0749-2170 |

DOIs | |

State | Published - 2003 |

### Publication series

Name | Institute of Mathematical Statistics Lecture Notes - Monograph Series |
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Volume | 43 |