The influence of the place-value structure of the Arabic number ...

indicated that Italian children’s estimates are in general more accurate than Austrian
children’s estimates. Additionally, the covariate (i.e., individual CFT-1 T-values) reached
significance [F(1, 223) = 13.83, p < .001].
% Estimation error
25
20
15
Figure 1: Mean estimation error in percent for
Italian and Austrian children. Error bars reflect 1
Standard Error of the Mean (SEM).
10
Italian children
Austrian children
Fit of simple linear, logarithmic and two-linear regression models:
The results of the Austrian children have already been described in great detail in
Moeller et al. (2009). Therefore, the results relevant for the present article will only be
summarized briefly. For the 0-to-100 scale logarithmic fitting was better as compared to the
simple linear one [adj. R² log = .70 vs. adj. R² lin =.61]. However, when contrasting the
logarithmic fitting to that of the two-linear model, the two-linear model accounted for a
reliably larger part of the variance than the logarithmic model [adj. R² two-lin = .81 vs. adj. R² log
= .70, see Figure 2, please note that for illustrating purposes the results of the item analysis
are depicted]. Furthermore, inspection of the children’s individual breakpoints showed that 95
out of 128 children assessed exhibited a breakpoint around 10 with the median of the
breakpoints at 11.33. While this is a little bit above the proposed breakpoint at 10 it
nevertheless corresponds nicely to the first two-digit numbers children had to position upon
the hypothetical number line.
99