. Author manuscript; available in PMC: 2017 Mar 24.

Published in final edited form as: Psychopharmacology (Berl). 2015 Sep 21;232(24):4493–4503. doi: 10.1007/s00213-015-4076-x

Table 2.

Differences between alcohol-dependent cases and controls before and after propensity-score matching based on age, gender, and education.

Variable	Samples	Bias (%)	Reduction in Bias (%)	Case vs. Control	Variance ratio (case/control)
Age	Unmatched	−38.5	70.5	t = 4.39^***	1.19
Age	Matched	−11.3		t = 1.10	1.27
Male (%)	Unmatched	56.9	53.8	Χ ² = 38.91^***	1.10
Male (%)	Matched	26.3		Χ ² = 6.09^**	1.03
Education	Unmatched	−84.5	86.3	z = 8.64^***	0.56
Education	Matched	−11.5		z = 1.31	0.96
Income	Unmatched	−105.8	15.6	z = 10.59^***	1.14
Income	Matched	−89.4		z = 8.42^***	1.16
Health Status	Unmatched	−27.0	−14.2	z = 3.15^***	1.06
Health Status	Matched	−30.9		z = 2.94^**	1.08
Depression Treatment (%)	Unmatched	30.3	−41.8	Χ ² = 11.74^***	1.25
Depression Treatment (%)	Matched	42.9		Χ ² = 16.88^***	1.30

Notes:

p<.05,

^**

p<.01,

^***

p<.001.

Where Bias is positive, the mean, median, or percentage is greater for cases than for controls. For the continuous variable Age, t-tests were used to compare cases and controls; for the ordinal variables Education, Income, and Health Status, the Mann-Whitney Rank Sums test was used; for the dichotomous variables (Males, and Depression Treatment), the Chi Square test was used.