Understanding sample size determination in nursing research.

Sample size determination is a natural consideration in the planning stages of most research studies. The purpose of this work is to provide an overview of modern methods of sample size determination and describe some of the challenges to be aware of and pitfalls to avoid in applying these various methods. Although sample size can be determined in many ways, the most commonly used approach has relied on classical hypothesis-based methods of power analysis. Several challenges often arise with traditional power analysis. For example, the statistical methods used in a power analysis may not adequately address the complexities of the data collected in a research study. The American Psychological Association currently accepts and endorses the use of two methods, power analysis and precision estimation, for sample size determination. Precision estimation is a viable alternative to the traditional power analysis approach. Recommendations for deciding on an approach are provided.