Table 2.

Results for all variables entered in the stepwise multiple regression analysis.

Variables included in the model	Standardized beta	t	Sign.
Break 10 (carry)	0.746	6.044	<0.001
Break 5	0.341	2.765	>0.01
Variables excluded from the model	Standardized beta	t	sign.
Problem size	−0.004	−0.037	0.970
Unit sum	−0.053	−0.263	0.794
Logarithmic sum	0.017	0.159	0.874
Logarithmic unit sum	−0.024	−0.144	0.886
Squared problem size	−0.007	−0.064	0.949
Product of summands	0.026	0.234	0.816
SSA	−0.012	−0.111	0.912
Parity of summand 1	0.028	0.245	0.807
Parity of summand 2	0.097	0.906	0.369
Break 10 × problem size	−0.027	−0.098	0.923
Break 5 × break 10 × problem size	−0.12	−0.433	0.667