A statistical model has a “lack-of-fit” if it fails to adequately explain the relationship between the x (dose) and y (response) variables. In a lack-of-fit statistical test, the null hypothesis is that the model fits the data. Thus, in these tests a significant p-value indicates that there is evidence that the model does not adequately explain the data, and so here we check that the p-value is greater than the significance threshold .
Significance thresholds commonly range from 0.05 to 0.5 depending on the desired stringency. The NTP recommends a threshold of 0.10.