A simple formula for sample size calculation in equivalence studies.

Area of Science:

• Biostatistics
• Pharmacokinetics
• Clinical Trials

Background:

• Bioequivalence and clinical equivalence assessments rely on specific statistical approaches.
• Current methods for determining sample size in equivalence studies often involve complex calculations.
• The power function of equivalence tests can be derived using either noncentral or central t-distributions.

Purpose of the Study:

• To propose a novel, simplified formula for sample size calculation in equivalence studies.
• To base the new formula on the central t-distribution for broader applicability.
• To offer a more practical alternative to existing sample size determination methods.

Main Methods:

• Derivation of a sample size formula utilizing the central t-distribution.
• Comparison of the proposed formula's properties against existing methods.
• Evaluation of the formula's ease of application in various equivalence study scenarios.

Main Results:

• A simple closed-form formula for sample size calculation has been developed.
• The proposed formula demonstrates superior properties compared to current approaches.
• The formula is designed for straightforward implementation in all types of equivalence studies.

Conclusions:

• The newly proposed formula provides an efficient and accessible method for sample size determination in equivalence studies.
• This simplified approach is expected to enhance the practical application of statistical methods in bioequivalence research.
• The formula's foundation in the central t-distribution ensures its relevance across diverse study designs.