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Washington State University Institutional Animal Care and Use Committee


Using our previous data as representative for this study, the power analysis was based on the prediction that treatment will evoke dose-related increases of the Y-intercept of the dose-effect curve relating the effect to the Y-variable. Accordingly, the power analysis was performed in terms of a two-factor ANOVA with two levels. The standard error of the estimate for the effect is 7% based upon a regression analysis of our existing dose-response data (group sizes were > 8). The effect size that we are designing the study to detect is 1.5 times this standard error. Using n= 10 per cell yields a power of 0.98 to detect this effect size.


The power analysis follows:

Power Analysis for ANOVA Designs

The power parameters you specified were:

  • a = ‘4’ (levels of factor for power)
  • b = ‘2’ (levels of factor(s) crossed with A)
  • delta = ‘1.5, 1.75, 2.0’ (effect size(s))
  • alpha = ‘0.05’ (significance level)


Power analysis for ANOVA designs

4x 2 layout Ha: T1=GM-Delta/2, T2=T3=…=T(k-1)=GM, Tk=GM+Delta/2 tested at Alpha= 0.050


DELTA (in units of sigma=Stdev)

N         1.500   1.750   2.000

10           0.982     0.997    0.999