| Study |
Country |
Ethnicity |
Experimental |
Control |
| Mean |
SD |
Number |
Mean |
SD |
Number |
| Nobuhiro Mikuni 1999 |
USA |
Caucasian |
147 |
23 |
3 |
139 |
18 |
3 |
| Nobuhiro Mikuni 1999 |
USA |
Caucasian |
106 |
16 |
3 |
97 |
17 |
3 |
| Ying Z 1999 |
USA |
Caucasian |
193 |
19 |
11 |
187 |
16 |
11 |
| Thomas L Babb 2000 |
USA |
Caucasian |
135 |
20 |
3 |
122 |
19 |
3 |
|
