He frequency of non-stuttered and total disfluencies in both talker groups. Fourth, parental concern about children’s stuttering was significantly associated with frequency of children’s stuttered disfluencies. These findings will be discussed immediately below. Number of disfluencies is not normally distributed–Present findings that frequency distributions of speech disfluencies were non-normal are consistent with earlier observations ( Davis, 1939; Johnson et al., 1963; Jones et al., 2006). The distributions of total, stuttered and non-stuttered disfluencies found in the present study conformed best to a negative binomial distribution. This type of distribution can be characteristic of variables that represent count (i.e., discrete) data. This distribution is often used to model theJ Commun Disord. 5-BrdU biological activity Author manuscript; available in PMC 2015 May 01.Tumanova et al.Pageoccurrence of relatively rare events, such as, in our case, the number of disfluencies children produce during a conversational sample. As applied to the present speech disfluency data set, negative binomial distribution of frequency of disfluencies signifies that there are more cases of mild stuttering among CWS and fewer cases of severe stuttering. From a data analytic standpoint, the fact that disfluency count data is not-normally distributed suggests that traditional inferential, parametric statistical MK-886 clinical trials methods such as ANOVA or ordinary least squares regression are inappropriate for these data. In such cases the mean and variance may not be good descriptors of the central tendency, leading to a potential increase of type 1 error. Going forward, when empirically studying the speech disfluenicies of children who do and do not stutter, it may be more appropriate to employ models that make assumptions that the data actually meet. Generalized linear models (GLM), as used in the present study, allow a choice among several distributions in which the response or dependent variable can have a non-normal distribution (Nelder Wedderburn, 1972). Table 10 presents frequency of disfluencies found in the present study and in previous studies of children who do and do not stutter. Although tempting, it is not possible to make absolute comparisons between the present dataset and other studies that also collected comparably large samples (e.g., Johnson et al., 1959; Yairi Ambrose, 2005; Yaruss, LaSalle, et al., 1998; Yaruss, Max, et al., 1998). This is due to the fact that some of these studies (e.g., Johnson et al., 1959) included children older than the age range of the present study and/or did not report a typically fluent comparison group (e.g., Yaruss, LaSalle, et al., 1998; Yaruss, Max, et al., 1998) and other studies employed a syllable-level measure of frequency (Ambrose Yairi, 1999; Yairi Ambrose, 2005).7 Thus, even though the present findings of mean values of 1.2 stuttered disfluencies per 100 words for CWNS and 9.2 for CWS is close to the mean values of 1.88 for CWNS and 11.5 for CWS reported by Johnson et al. (1959) and the mean value of 10.67 for CWS reported by Yaruss, LaSalle, et al. (1998) readers should be aware that differences in age range of participants and/or measurement methodology render absolute comparisons problematic. Likewise, there are challenges with making direct comparisons between the present relatively large dataset and other smaller datasets, since larger sample sizes generally lead to increased precision when estimating unknown parameters such.He frequency of non-stuttered and total disfluencies in both talker groups. Fourth, parental concern about children’s stuttering was significantly associated with frequency of children’s stuttered disfluencies. These findings will be discussed immediately below. Number of disfluencies is not normally distributed–Present findings that frequency distributions of speech disfluencies were non-normal are consistent with earlier observations ( Davis, 1939; Johnson et al., 1963; Jones et al., 2006). The distributions of total, stuttered and non-stuttered disfluencies found in the present study conformed best to a negative binomial distribution. This type of distribution can be characteristic of variables that represent count (i.e., discrete) data. This distribution is often used to model theJ Commun Disord. Author manuscript; available in PMC 2015 May 01.Tumanova et al.Pageoccurrence of relatively rare events, such as, in our case, the number of disfluencies children produce during a conversational sample. As applied to the present speech disfluency data set, negative binomial distribution of frequency of disfluencies signifies that there are more cases of mild stuttering among CWS and fewer cases of severe stuttering. From a data analytic standpoint, the fact that disfluency count data is not-normally distributed suggests that traditional inferential, parametric statistical methods such as ANOVA or ordinary least squares regression are inappropriate for these data. In such cases the mean and variance may not be good descriptors of the central tendency, leading to a potential increase of type 1 error. Going forward, when empirically studying the speech disfluenicies of children who do and do not stutter, it may be more appropriate to employ models that make assumptions that the data actually meet. Generalized linear models (GLM), as used in the present study, allow a choice among several distributions in which the response or dependent variable can have a non-normal distribution (Nelder Wedderburn, 1972). Table 10 presents frequency of disfluencies found in the present study and in previous studies of children who do and do not stutter. Although tempting, it is not possible to make absolute comparisons between the present dataset and other studies that also collected comparably large samples (e.g., Johnson et al., 1959; Yairi Ambrose, 2005; Yaruss, LaSalle, et al., 1998; Yaruss, Max, et al., 1998). This is due to the fact that some of these studies (e.g., Johnson et al., 1959) included children older than the age range of the present study and/or did not report a typically fluent comparison group (e.g., Yaruss, LaSalle, et al., 1998; Yaruss, Max, et al., 1998) and other studies employed a syllable-level measure of frequency (Ambrose Yairi, 1999; Yairi Ambrose, 2005).7 Thus, even though the present findings of mean values of 1.2 stuttered disfluencies per 100 words for CWNS and 9.2 for CWS is close to the mean values of 1.88 for CWNS and 11.5 for CWS reported by Johnson et al. (1959) and the mean value of 10.67 for CWS reported by Yaruss, LaSalle, et al. (1998) readers should be aware that differences in age range of participants and/or measurement methodology render absolute comparisons problematic. Likewise, there are challenges with making direct comparisons between the present relatively large dataset and other smaller datasets, since larger sample sizes generally lead to increased precision when estimating unknown parameters such.
