The LnGM radon was used on the y axis because the uncertainty
(expressed by the LnGSD) had to be symmetrically distributed either side of each data point for the
WTLS regression analysis. There is little difference between the indoor radon concentrations
predicted by the GM indoor radon – eRa226 and LnGM indoor radon – eRa226 regression lines at
the upper limits of the data used to construct the models. However, at the higher concentrations
which may in some circumstances be encountered above near-surface radioactive waste disposal
sites, the LnGM indoor radon – eRa226 regression models predict higher radon concentrations than
the GM indoor radon – eRa226 models, when the intercepts for both types of models are
unconstrained.