(b).

Number	First author	Statistics for each study					Difference in means and 95% CI	Relative weight
		Difference in means	Standard error	Variance	Z value	P value
5 6 9	Wu (2008) [12] Baptista (2007) [13] Baptista (2006) [16] Total	−5.000 −1.200 −0.800 −1.331	2.051 0.698 0.939 0.540	4.207 0.487 0.882 0.292	−2.438 −1.719 −0.852 −2.464	0.015 0.086 0.394 0.014		6.94 59.94 33.12 100.00

Heterogeneity: Q = 3.55; df = 2; P = 0.17; I ² = 43.74.