MEASURES OF BIMO DAL ITY One useful

MEASURES OF BIMO DAL ITY

One useful index of this disjunct character is Ashman’s D in (2)—a measure of bimodality expressed by the absolute difference of the means divided by the square root of the average of the two standard deviations (Ashman, Bird, & Zepf, 1994; Gnedin, 2010).


(2)



D ; j m1 m2 j
[(s2 þ s2 =2]1=2

1 2


The value of D for distance along the front diagonal in Figure 7 is 3.439. For a clear separation like that of Jean B., bimodality ranges between 3 and 4.
Figure 8 displays the distribution of this bimodality measure for all PNC speakers with more than 7 tokens of /æh/, including 293 whites and 33 African American speakers. The range is from close to 0.02 to 7.91. It is evident that the black columns are heavily concentrated in the lower end of the distribution. From the diagram, it would appear that the African American speakers have absorbed the short-a system of one particular subtype of the white mainstream pattern, presumably the people they are in closest contact with. But this proves to be an understatement of the differences. The whites with low bimodality are actually those found by LRF to have switched abruptly from the traditional split short-a system to the nasal system, in which all short-a before nasal consonants are fronted and raised along the front diagonal and all others are retained in low front position (Labov et al., 2006:174–175). This shift to the nasal system is most characteristic of college students in nationally oriented universities and high school students oriented in that direction. Figure 9 shows the two aspects of this conversion from the traditional Philadelphia system in the speech of a Penn

Results (Indonesian) 1:

UKURAN BIMO DAL ITY Indeks berguna satu karakter sebaran ini adalah Ashman's D di (2)-ukuran bimodality yang diungkapkan oleh perbedaan mutlak sarana dibagi dengan akar kuadrat dari rata-rata dua standar deviasi (Ashman, burung, & Zepf, 1994; Gnedin, 2010). (2) D; j m1 m2 j [(s2 þ s2 = 2] 1 = 2 1 2Nilai d untuk kaki, di sepanjang bagian depan diagonal di gambar 7 adalah 3.439. Untuk pemisahan jelas seperti Jean B., bimodality berkisar antara 3 dan 4.Figure 8 displays the distribution of this bimodality measure for all PNC speakers with more than 7 tokens of /æh/, including 293 whites and 33 African American speakers. The range is from close to 0.02 to 7.91. It is evident that the black columns are heavily concentrated in the lower end of the distribution. From the diagram, it would appear that the African American speakers have absorbed the short-a system of one particular subtype of the white mainstream pattern, presumably the people they are in closest contact with. But this proves to be an understatement of the differences. The whites with low bimodality are actually those found by LRF to have switched abruptly from the traditional split short-a system to the nasal system, in which all short-a before nasal consonants are fronted and raised along the front diagonal and all others are retained in low front position (Labov et al., 2006:174–175). This shift to the nasal system is most characteristic of college students in nationally oriented universities and high school students oriented in that direction. Figure 9 shows the two aspects of this conversion from the traditional Philadelphia system in the speech of a Penn