(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
2 3	Narula (2010) [9] Afshar (2009) [10] Total	−2.500 −2.190 −2.405	0.990 1.491 0.825	0.980 2.223 0.680	−2.525 −1.469 −2.916	0.012 0.142 0.004		69.41 30.59  100.00

Heterogeneity: Q = 0.03; df = 1; P = 0.86; I ² = 0.00.