The group-related differences on the measures assessing lexical production (i.e., Naming, Semantic Fluency, Speech Rate, Percentage of Semantic Paraphasias produced in the Nest Story description task) were analyzed with a series of independentsamples
t-tests. The level of statistical significance was set at p < .0125 (.05/4 dependent variables) after Bonferroni correction for multiple comparisons. Effect sizes were calculated in terms of Cohen’s d (Cohen, 1988). This is computed as the difference between the mean of the control group and that of the group of participants with SLI divided by the pooled sample
standard deviation. The role played by verbal working memory on linguistic performance was controlled by performing an
additional series of One-Way ANCOVAs with the scores at the NWR subtest of the BVL_4-12 as covariate. Table 2 reports the
results of these analyses showing the level of group-related significance before (t-tests) and after covariation (ANCOVAs).
When verbal working memory was not included in the analysis as covariate, the independent samples t-tests showed that
the group of children with SLI had impaired performance on all of these measures: Naming (t(59) = 2.920; p < .005;
d = .75); Speech Rate (t(61) = 3.070; p < .003; d = .77); Semantic Fluency (t(62) = 2.667; p < .010; d = .67), Percentage
of Semantic Paraphasias (t(44) = 4.290; p < 001; d = 1.08). Interestingly, when the analyses were rerun controlling for NWR,
only the group-related differences in Semantic Fluency and Speech Rate were no longer significant (p = .163 and p = .036,
respectively), while those pertaining Naming (p < .009) and the Percentage of Semantic Paraphasias (p < .001) survived.