In this paper we discuss statistical inference for a two-by-two table under inverse sampling, where the total number of cases is ﬁxed by design. We demonstrate that the exact unconditional distributions of some relevant statistics diﬀer from the distributions under conventional sampling, where the sample size is ﬁxed by design. This permits us to deﬁne a simple unconditional alternative to Fisher’s exact test. We provide an asymptotic argument including simulations to demonstrate that there is little power-loss associated with the alternative test when the expected response rates are rare. We then apply the method to design a clinical trial in cataract surgery, where a rare side eﬀect occurs in one in one-thousand patients. Objective of the trial is to demonstrate that adjuvant treatment with an antibiotic will reduce this risk to one in two-thousand. We use an inverse sampling design and demonstrate how to set this up in a sequential manner. Particularly simple stopping rules can be deﬁned when using the unconditional alternative to Fisher’s exact test.

Exact and Asymptotic Inference in Clinical Trials with Small Event Rates under Inverse Sampling / Heimann, G.; Von Tress, M.; Gasparini, Mauro. - ELETTRONICO. - (2014), pp. 1-42.

Exact and Asymptotic Inference in Clinical Trials with Small Event Rates under Inverse Sampling

Abstract

In this paper we discuss statistical inference for a two-by-two table under inverse sampling, where the total number of cases is ﬁxed by design. We demonstrate that the exact unconditional distributions of some relevant statistics diﬀer from the distributions under conventional sampling, where the sample size is ﬁxed by design. This permits us to deﬁne a simple unconditional alternative to Fisher’s exact test. We provide an asymptotic argument including simulations to demonstrate that there is little power-loss associated with the alternative test when the expected response rates are rare. We then apply the method to design a clinical trial in cataract surgery, where a rare side eﬀect occurs in one in one-thousand patients. Objective of the trial is to demonstrate that adjuvant treatment with an antibiotic will reduce this risk to one in two-thousand. We use an inverse sampling design and demonstrate how to set this up in a sequential manner. Particularly simple stopping rules can be deﬁned when using the unconditional alternative to Fisher’s exact test.
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2014
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Utilizza questo identificativo per citare o creare un link a questo documento: `https://hdl.handle.net/11583/2563549`