R Models.” The model tested for the main effects of each covariate and also for the interaction of group by gender as described below. To assess whether parental concern about AICA Pepstatin manufacturer RibosideMedChemExpress AICAR children’s stuttering is associated with examiner’s judgment of stuttering we employed a logistic regression analysis.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript3. ResultsAnalyses of descriptive data/group characteristics are reported first, followed by statistical tests of each hypothesis. 3.1. Descriptive analyses of the data: group differences in age, gender and speechlanguage abilities Table 1 provides descriptive statistics for each talker group for language variables and age, all of which were normally distributed. Normal distributions are common for standardizedJ Commun Disord. Author manuscript; available in PMC 2015 May 01.Tumanova et al.Pagetests with many items. Multivariate ANOVA was performed to assess between-group differences on each variable.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptResults indicated that preschool-age CWS, when compared to preschool-age CWNS, show significantly lower scores on PPVT (F = 11.71, df = 1, p = .001), EVT (F = 11.96, df = 1, p = .001), and TELD receptive subtest standard scores (F = 13.47, df = 1, p < .001). There was also a significant difference in age (F = 12.26, df = 1, p = .001) with CWS being younger than CWNS, and our sample included 1.4 times more male CWS (n = 172) than male CWNS (n = 125). These differences between preschool-age CWS and their CWNS peers give these variables potential leverage to influence measures of speech disfluency. As mentioned above, to control for possible effects of those differences on stuttered and non-stuttered disfluencies, each of these possible confounds was entered in the statistical model as a covariate. There were no significant between-group differences on the GFTA, TELD expressive subtest standard scores or SES. 3.2. Hypothesis 1: non-normality of distribution of speech disfluencies Table 2 provides descriptive statistics (percentiles) for both talker groups for all dependent variables (i.e., stuttered, non-stuttered and total disfluencies). Results of the Shapiro ilk test of normality indicated that the distributions for all three variables were non-normally distributed. The statistics for distribution of stuttered disfluencies were as follows: W = .954, df = 244, p < .0001 for CWNS and W = .861, df = 228, p < .0001 for CWS, with significance of the Shapiro ilk's test indicating non-normality of distributions for both talker groups. The statistics for distribution of non-stuttered disfluencies were as follows: W = .914, df = 244, p < .0001 for CWNS and W = .945, df = 228, p < .0001 for CWS, also nonnormal distributions for both talker groups. The statistics for distribution of total disfluencies were as follows: W = .947, df = 244, p < .0001 for CWNS and W = .897, df = 228, p < .0001 for CWS, again, non-normal distributions for both talker groups. Consistent with these analytical findings, histograms for each of the three dependent variables (Fig. 1(A)?C)) show that the data were non-normally distributed. The skewed distributions resembled a Poisson distribution but the variance was excessive (larger than the mean). For this reason a negative binomial distribution was used to model the distributions. In brief, results of both formal and informal assessment of normality supported hypothesis 1, that is, stuttered,.R Models." The model tested for the main effects of each covariate and also for the interaction of group by gender as described below. To assess whether parental concern about children's stuttering is associated with examiner's judgment of stuttering we employed a logistic regression analysis.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript3. ResultsAnalyses of descriptive data/group characteristics are reported first, followed by statistical tests of each hypothesis. 3.1. Descriptive analyses of the data: group differences in age, gender and speechlanguage abilities Table 1 provides descriptive statistics for each talker group for language variables and age, all of which were normally distributed. Normal distributions are common for standardizedJ Commun Disord. Author manuscript; available in PMC 2015 May 01.Tumanova et al.Pagetests with many items. Multivariate ANOVA was performed to assess between-group differences on each variable.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptResults indicated that preschool-age CWS, when compared to preschool-age CWNS, show significantly lower scores on PPVT (F = 11.71, df = 1, p = .001), EVT (F = 11.96, df = 1, p = .001), and TELD receptive subtest standard scores (F = 13.47, df = 1, p < .001). There was also a significant difference in age (F = 12.26, df = 1, p = .001) with CWS being younger than CWNS, and our sample included 1.4 times more male CWS (n = 172) than male CWNS (n = 125). These differences between preschool-age CWS and their CWNS peers give these variables potential leverage to influence measures of speech disfluency. As mentioned above, to control for possible effects of those differences on stuttered and non-stuttered disfluencies, each of these possible confounds was entered in the statistical model as a covariate. There were no significant between-group differences on the GFTA, TELD expressive subtest standard scores or SES. 3.2. Hypothesis 1: non-normality of distribution of speech disfluencies Table 2 provides descriptive statistics (percentiles) for both talker groups for all dependent variables (i.e., stuttered, non-stuttered and total disfluencies). Results of the Shapiro ilk test of normality indicated that the distributions for all three variables were non-normally distributed. The statistics for distribution of stuttered disfluencies were as follows: W = .954, df = 244, p < .0001 for CWNS and W = .861, df = 228, p < .0001 for CWS, with significance of the Shapiro ilk's test indicating non-normality of distributions for both talker groups. The statistics for distribution of non-stuttered disfluencies were as follows: W = .914, df = 244, p < .0001 for CWNS and W = .945, df = 228, p < .0001 for CWS, also nonnormal distributions for both talker groups. The statistics for distribution of total disfluencies were as follows: W = .947, df = 244, p < .0001 for CWNS and W = .897, df = 228, p < .0001 for CWS, again, non-normal distributions for both talker groups. Consistent with these analytical findings, histograms for each of the three dependent variables (Fig. 1(A)?C)) show that the data were non-normally distributed. The skewed distributions resembled a Poisson distribution but the variance was excessive (larger than the mean). For this reason a negative binomial distribution was used to model the distributions. In brief, results of both formal and informal assessment of normality supported hypothesis 1, that is, stuttered,.
