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

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53, 64, 75, 82, and 95) we first computed <strong>the</strong> mean estimation error over all participating<br />

children and <strong>the</strong>n subtracted each child’s individual estimation error from it. A negative<br />

difference thus indicated that a child underestimated a given <strong>number</strong> even stronger than<br />

expected by <strong>the</strong> mean estimation error whereas a positive difference indicated that a child<br />

underestimated a given <strong>number</strong> less than expected by <strong>the</strong> mean estimation error, thus<br />

reflecting a relative overestimation. Additionally, to ensure that possible language differences<br />

were not driven by differences in <strong>the</strong> distribution <strong>of</strong> <strong>the</strong> computed difference scores between<br />

German- and Italian-speaking children a z-transformation <strong>of</strong> <strong>the</strong>se individual difference<br />

scores was conducted. Subsequently, we directly tested <strong>the</strong> hypo<strong>the</strong>sis that German-speaking<br />

children’s under-/overshoot should be more pronounced and thus <strong>the</strong> difference between<br />

items provoking ei<strong>the</strong>r <strong>of</strong> it should be reliably larger for <strong>the</strong>m using a t-test.<br />

RESULTS<br />

CFT-1: <strong>The</strong> results <strong>of</strong> <strong>the</strong> CFT-1 are presented first as <strong>the</strong>y have an <strong>influence</strong> on <strong>the</strong><br />

following analyses. A t-test for independent samples revealed a significant difference <strong>of</strong> T-<br />

<strong>value</strong>s in CFT-1 between <strong>the</strong> two countries, t(223) = 10.32, p < .001, with Italian children<br />

showing a significant lower average T-<strong>value</strong> (48.27, SD = 6.5) than Austrian children (58.59,<br />

SD = 8.1). We examined whe<strong>the</strong>r this effect was due to <strong>the</strong> fact that <strong>the</strong> Italian children were<br />

younger than <strong>the</strong> Austrian children. However, even when taking <strong>the</strong> age group instead <strong>of</strong><br />

grade as reference in <strong>the</strong> CFT-1, Italian children still scored significantly lower. For that<br />

reason, individual T-<strong>value</strong>s were included as a covariate in all fur<strong>the</strong>r analyses.<br />

Overall estimation accuracy:<br />

An univariate ANCOVA on each child’s mean percent absolute error revealed a<br />

reliable main effect <strong>of</strong> language for <strong>the</strong> 0-to-100 scale [F(1, 223) = 7.97, p < .01] with a mean<br />

estimation error <strong>of</strong> 17.78% for Italian and 21.06% for Austrian children (see Figure 1). This<br />

98

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