We considered additional models using the remaining
socio-economic and population variables, and found
that none offered a substantial improvement on the base model with IER score as a non-linear variable and the percentage of non-Indigenous persons as a linear variable
(Supplement, Fig. S3). Therefore, we concluded that it
was the best model (R2 = 6.4%). Fig. 3 gives the final predictions
from the best model. It shows a decrease in predicted
NO2 levels with increasing IER scores for all but the bottom
5% of SA1s. Predicted NO2 also decreased slightly as the
percentage of non-Indigenous persons increased. The
caveat to this result is that most areas have a high percentage
of non-Indigenous persons with a small number of
areas having a low percentage, hence the predictions interpolate
an area where there is no data. Parameter estimates
are in Table 2 and show that both parameters were statistically
significant and the 95% credible intervals do not
contain zero.