Table 2. Mean acoustic values of /z/ production by speaker group

Table 2. Mean acoustic values of /z/ production by speaker group
Speakergroup	Fricationduration	CVduration	Fricationratio
NATIVE	132.92	317.25	44.42
HIGH	84.17	203.70	40.37
MID	63.93	231.25	30.35
LOW	69.21	232.61	30.31

Total analyzed items per group: NATIVE (n=13), HIGH (n=50), MID (n=50), and LOW (n=48). Among the Korean EFL learners, the number of errors produced is 15 (HIGH), 21 (MID), and 33 (LOW).