Statistics in Animal Experiments

Background: The Guide for the Care and Use of Laboratory Animals (2011) states, "...whenever possible, the number of animals and experimental group sizes should be statistically justified (e.g., provision of a power analysis)."

In the IRP, the number of animals requested for studies will be based on a statistical justification documented by the PI that includes:

1. A brief description of the statistical tests used,
2. An experimental design informed by sound statistical methods, and
3. An assessment of the biological importance of the results.

For studies where there is no preliminary data, justification should be given for the number of animals requested based on how large an effect size is anticipated to signify biological importance.

Consultations between statisticians and scientists are encouraged as part of the study design process.

NIH Statistical Resources:

• NIH Library - Statistical Support Services
• NIH Clinical Center - Biostatistics and Clinical Epidemiology Service
• NIH Equipment, Software, and Tools
• NIH Statistics Classes and Services

External Statistical Resources:

• NC3Rs Experimental Design Assistant
• ARRIVE Guidelines - Statistical Methods
• Norecopa - Design and Reporting of Animal Experiments

This page was last updated on Wednesday, August 2, 2023