Table 2. Mean Absolute Errors (MAEs) in the Predicted Atomization Enthalpies of the Constitutional Isomers of C₇H₁₀O₂ from OM2 (N_train = 0) and ML-OM2//OM2 Calculations at OM2 Geometries^a.

Ntrain	training set	test set
0		6.30
10	0.00	6.31
100	0.00	5.46
1000	0.00	2.88
2000	0.00	2.29
3000	0.00	1.96
4000	0.00	1.81
5000	0.00	1.72

^aSee the text for details. MAEs are given in kcal/mol for N_train molecules in the training sets and for 6095 – N_train molecules in the test sets.