Sample size calculation

Using t = 2 for a first approximation (P=0.05), it can be shown that n = 13.3 or, rounding up to the nearest integer, n =14. Sketching out the analysis of variance table this would give:

Source of variation	d.f
Batch	2
Diet	2
Covariate	1
Residual	36
Total	41

The 5% t-value with 36 degrees of freedom is 2.03. Repeating the above calculation but replacing t by this value, the new result is n = 13.7. This confirms that 14 animals will be necessary for each of the diets C and A+B in order to demonstrate a significant effect of supplementation with calliandra over the 60 days.