Sample Size Determination for Alternate Periods of Use Study Designs with Binary Responses

• Activity Number: 582
• Type: Contributed
• Date/Time: Wednesday, August 3, 2011 : 2:00 PM to 3:50 PM
• Sponsor: Biopharmaceutical Section
• Author(s): Jorge Morel*+ and Nagaraj K. Neerchal
• Companies: The Procter and Gamble Company and University of Maryland at Baltimore County
• Keywords: Cross-over Designs ; Repeated Measures ; Menstrual Studies ; Diaper Studies ; Exchangeable Correlation ; Power

Abstract

We consider several study designs that arise in practice, which are variations of standard cross-over designs. Often, they may result from modifications of standard cross-over designs due to practical considerations. Characteristic features of these studies are: a) treatments consist of external use of products with little or no possibility of carry over effects, and b) the periods of use are dictated by the subjects or by some specific event such as diaper leakage or menstrual flow. We consider a number of such study designs for estimating the difference in the efficacy of two treatments or test products. We provide brief descriptions of studies to motivate the study design, the underlying data structure, and computations of the variances of the usual unbiased estimators of the difference in efficacy, and the sample size formulas. The situations considered here cover a number of popular cross-over designs. Objective of our work is to provide guidance to a wide audience on how to answer the sample size question for their own non-standard situations. We conclude with a simulation study conducted to investigate the impact of estimation on the sample size determination.