Analyze the TLY21 data in Table 8.1 with the high
treatment group omitted. Verify that both the untransformed and square‐
root transformed responses satisfy the normality and variance homogeneity
requirements to use Williams’ test. Compute the NOEC from that test and from
the Jonckheere–Terpstra and Dunnett’s tests. Determine whether suitable
regression models can be fit to these data, and, if so, provide point and
interval estimates of EC10 and ECx for other choices of x where defensible
estimates are possible