ABSTRACT
the speech quality parameters have been provided as one of the main factors for determining the nature and volume of language impairment. We standardize the measures of total numbers of word, mean length of utterance [MLU] and mean length of 5 long sentences in normal Semnanian 2 to 5 years' old children's spontaneous language samples, which elicit by conversation method. Since in Iran the treatment of childhood language disorders achieve in base of clinician experiences and/or sometimes by English language norms so it is necessary that determine such norms of the speech quality parameters for Persian language children. In the search, we studied 580 normal Semnanian 2 to 5 years old Persian language children. The examiner used pictures and storybooks for eliciting the descriptive language sample and open- ended question for eliciting the free language sample. Children's language samples were recorded in tape script. Later, these oral samples were written on the paper by international transcribe. Then we calculated the measures of the speech quality parameters and analyzed them by statistical tests. According to the findings of this study, the norm of total numbers of word, MLU and mean length of 5 long sentences were determined for Semnanian 2 to 5 years old children. Also, the findings showed increasing in total number of word, MLU and mean length of 5 long sentences throughout arising the child's age from 2 to 5 years old. The findings indicate that the child's age influences on these speech quality parameters in base of type of speech [language sampling method]. Therefore, the process of increasing the measures of these speech quality parameters varies in aspect of child's type of speech