The reliability of data may be determined either by correlating odd-even frequencies of speech sounds or by the method of the percent of agreement of the items. In the following both methods will be applied to a sample of the speech sounds of infants. The sample upon which the analyses are based are sixty records of infant speech sounds from a total of over a thousand records from the first to the thirtieth month of life. Two records per month were selected randomly by means of a table of random numbers. In this sample 13 vowel and 26 consonant sounds were found
