Table 2 Risk of bias in individual studies
1 | 2 | 3 | 4 | 5 | 6 | Global Judgment | |
|---|---|---|---|---|---|---|---|
Browne 2002 | yes | yes | yes | yes | yes | no | low |
deMello 2001 | unclear | unclear | yes | unclear | yes | no | medium |
Keller 2000 | yes | yes | yes | yes | yes | yes | low |
Kocsis 2009 | yes | yes | yes | yes | no | yes | low |
Markowitz 2005 | yes | unclear | yes | yes | yes | yes | low |
Miller 1999 | no | yes | unclear | unclear | no | no | high |
Ravindran 1999 | yes | unclear | yes | yes | no | yes | medium |
Schramm 2008 | yes | unclear | yes | yes | yes | yes | low |
Summary “yes” | 6/8 | 4/8 | 7/8 | 6/8 | 5/8 | 5/8 | 4/8 |