Study Country Ethnicity Experimental Control Mean SD Number Mean SD Number Iniad M Najm 2000 USA Caucasian 6.3 1.78 5 5.7 1.33 5 Jie Zheng 2011 USA Caucasian 5 4.44 20 3.5 2.96 10

Table 4: Outcomes of included studies under experimental methods (NR1, ICC).