Table 3. Balance of the Propensity Scores for LME exposure: Results from PSM.

Groups	Non-Exposed to LME (A) N	Exposed to LME (B) N	Mean Propensity Score±SD (Range)	Number of Balanced Blocks#	Net Difference (B-A) Using “Atts” Command
Female students (N = 225)	150	75	0.62±0.36 (0.002–1.000)	5 blocks	20.0% (P<0.05)
Male students (N = 196)	148	48	0.48±0.20 (0.03–0.98)	7 blocks	9%(P<0.05)
P (χ2) for comparing proportions between different female and male groups					P<0.01

^#pscore statistics indicate that there is no statistical difference between A and B within each stratum (p>.05), meaning that propensity scores balanced at 5 strata for females and 7 strata for males.