Plot of Coefficient of variation (CoV) of AFC values for four efficiency estimation methods. For each method, primer CoV values for each of the 78 primers considered are sorted from largest to smallest. A precise efficiency estimate results in a lower CoV. The curves for clustered and individually determined efficiencies are overlapping. This demonstrates that using just a small number of average cluster efficiencies is comparable to using individual primer efficiencies, i.e. the differences in efficiency within each cluster are negligible.