Power Analysis of Simulated Organ Weight Data

Music City Center 

In research involving laboratory animals, adhering to ethical guidelines that rationalize the required number of animals is essential for ensuring responsible research practices. Using reference rat organ weight data from the National Toxicology Program (NTP), we conducted a simulation and power analysis to determine the statistical power of Jonckheere's trend test with Williams and Dunnett multiple comparison procedures, the NTP standard approach for evaluating these data. We also determined the appropriate sample size to achieve desired power (≥80%) with an α=0.05 significance threshold. The simulation evaluated select organ weight endpoints across varying effect sizes of biological interest, across four simulated dose groups, under assumptions of normality and heteroscedasticity between groups. Results for both power and sample size varied across endpoints due to differences in means and standard deviations observed in the pilot data. These findings prompt broader discussions regarding 1) the varying power requirements across endpoints within a single study, and 2) marrying sample sizes derived from power analyses with considerations of time, cost, and ethical constraints.

Statistical power

Simulations

Effect size

Sample size 

Government Statistics Section