Hello, I'm interested in Songbird to check the correlation between microbial relative abundance and ferritin level. However, I can not get the best model because Pseudo-Q-squared is very low (negative value = -0.008)

using songbird code =>

qiime songbird multinomial

--i-table filtered_table_fea_final.qza

--m-metadata-file metadata.tsv

--p-formula "ferritinvalue"

--p-epochs 20000

--p-batch-size 20

--p-differential-prior 0.5

--p-summary-interval 1

--o-differentials differentials.qza

--o-regression-stats regression-stats.qza

--o-regression-biplot regression-biplot.qza

I tried to adjust parameters in many times but I can not get pseudo-Q-squared in positive. Could you please suggest me how to adjust them?

Thanks in advance.