. Author manuscript; available in PMC: 2021 Nov 1.

Published in final edited form as: Comput Toxicol. 2020 Nov 1;16(November 2020):10.1016/j.comtox.2020.100139. doi: 10.1016/j.comtox.2020.100139

Table 1.

Summary of the dataset and random forest model performance metrics for different study types and species combinations used in this study. Only the combinations with more than 50 unique chemicals were used in this analysis. The mean standard deviation per combination reflects the underlying variability in the data and can be thought of as a theoretical lower bound on RMSE i.e. we can expect the RMSE to be higher than this.

Study Type	Species	Total number of effect level values	Number of unique chemicals with curated structure and descriptors	Training-Test set split	Theoretical lower bound on RMSE (Mean standard deviation of effect level values, Figure 2)	Random Forest Model Performance Metrics
						Internal Training Set (5-fold cross-validation)			External Test Set
						RMSE	RMSE/σ	R²	RMSE	RMSE/σ	R²
Chronic (CHR)	Rat	7172	1129	903-226	0.51	0.93	0.76	0.43	0.93	0.82	0.33
	Mouse	4029	720	576-144	0.50	0.86	0.84	0.29	0.96	0.82	0.33
	Rat, Mouse	11201	1236	988-248	0.55	0.94	0.78	0.39	0.92	0.77	0.40
Subchronic (SUB)	Rat	36017	3199	2559-640	0.48	0.81	0.82	0.33	0.86	0.85	0.28
	Mouse	5030	723	578-145	0.50	0.88	0.83	0.31	0.86	0.80	0.37
	Rabbit	1516	415	332-83	0.49	0.96	0.96	0.08	0.83	0.90	0.20
	Rat, Mouse, Rabbit	42563	3306	2644-662	0.50	0.83	0.83	0.31	0.80	0.82	0.33
Reproductive (REP)	Rat	5446	841	672-169	0.49	0.79	0.80	0.36	0.76	0.84	0.30
	Mouse	505	87	69-18	0.36	1.80	1.09	−0.19	0.88	0.71	0.50
	Rat, Mouse	5951	889	711-178	0.49	0.91	0.86	0.26	0.79	0.83	0.31
Developmental (DEV)	Rat	6021	930	744-186	0.41	0.80	0.92	0.16	0.78	0.89	0.20
	Mouse	704	116	92-24	0.34	1.05	0.96	0.09	0.80	1.05	−0.09
	Rabbit	3220	491	392-99	0.38	0.76	0.89	0.20	0.88	0.95	0.10
	Rat, Mouse, Rabbit	9945	1004	803-201	0.42	0.76	0.89	0.29	0.80	0.86	0.26
Subacute	Rat	946	160	128-32	0.58	0.92	0.98	0.05	1.04	1.05	−0.10
ALL (CHR, SUB, REP, DEV, SAC)	All (Rat, Mouse, Rabbit)	71020	3632	2905-727	0.53	0.82	0.82	0.32	0.81	0.80	0.36
^*ALL (CHR, SUB, REP, DEV, SAC)	All (Rat, Mouse, Rabbit)	71020	3632	8349-2088	-	0.67	0.65	0.54	0.70	0.64	0.57

The numbers in this row reflect the final model (Figure 5) which use study type and species as additional descriptors and so each chemical is used more than once in the training dataset as separate instances reflected in the much larger size of training and test sets.