Table 1.

Coefficients of determination for the relationship between breaking stress and each prediction measure within each species.

Measure	Red maple		Callery pear		Sawtooth oak		Mean R²
Measure	n	R²	n	R²	n	R²	Mean R²
Diameter ratio	89	0.56	106	0.59	87	0.56	0.57
Branch diameter^{^z}/attachment width	73	0.51	105	0.65	87	0.56	0.57
Trunk diameter^{^y}/attachment width	73	0.36	105	0.53	87	0.49	0.46
Rough branch diameter/attachment width	73	0.37	105	0.40	87	0.38	0.38
Branch angle	89	0.17	106	0.35	87	0.47	0.33
Branch bark ridge angle	87	0.15	106	0.31	87	0.36	0.27
Trunk diameter^{^x}/attachment width	71	0.24	102	0.02	87	0.34	0.20
Attachment length	86	0.11	106	0.41	87	0.15	0.22
Attachment angle	89	0.06	106	0.31	87	0.27	0.21
Branch bark ridge length	87	0.11	106	0.38	87	0.13	0.21
Specific gravity	88	0.01	106	0.01	87	0.18	0.06
Percent area of included bark	88	0.07	106	N/A^{^w}	87	0.08	N/A^{^w}
Mean		0.22		0.29		0.29