Fig. 4

Case study 4. Eggshell thickness (ESThick). HCD data from 1993 to 1995 are displayed to the left of the concurrent study, while data from 1996 to 1999 are on the right. One high outlier is evident in the control and two low outliers are evident at 100 ppm. The mean response at 25 ppm is below the HCD lower confidence bound. The control mean response is near the HCD upper bound and mean responses in the two highest treatments are near the HCD lower bound. The median responses in all treatment groups were below the HCD lower bound. There is no question about the statistical significance of the decreased thickness in the three treatment groups. Nor is there any question about whether the mean or median responses are below the HCD lower bound. The question is whether such small differences are biologically important. EFSA guidance indicates not