Appendix C.
Covariate balance: means of covariates, before and after matching on propensity scores
| Before matching | After matching | |||||||
|---|---|---|---|---|---|---|---|---|
| College Degree |
No coll. deg |
% bias |
No coll. deg |
% bias |
||||
| Age at Wave 4 | 28.34 | 28.46 | *** | −6.9 | 28.29 | 2.9 | ||
| Female | .57 | 0.47 | *** | 20.0 | .54 | ** | 7.2 | |
| Race (White) | ||||||||
| Black | .18 | .21 | *** | −8.7 | .18 | .3 | ||
| Hispanic | .11 | .17 | *** | −18.6 | .13 | ** | −6.3 | |
| A/PI | .07 | .04 | *** | 16.1 | .10 | *** | −11.5 | |
| Other | .00 | .01 | *** | −8.9 | .00 | .9 | ||
| Born in the U.S. | .93 | .94 | −1.2 | .92 | * | 6.4 | ||
| Household smoker | .31 | .51 | *** | −41.3 | .31 | −1.0 | ||
| Parent smoker | .58 | .68 | *** | −22.1 | .60 | −3.6 | ||
| Frequency of parent HED | 1.16 | 1.28 | *** | −16.0 | 1.18 | −2.6 | ||
| Parent educational attainment | 14.57 | 12.66 | *** | 84.1 | 14.57 | −.3 | ||
| Mom is professional | .42 | .23 | *** | 42.1 | .42 | .8 | ||
| Dad is professional | .81 | .70 | *** | 26.7 | .81 | .3 | ||
| Income-to-needs ratio (400%+) | ||||||||
| Below 100% | .06 | .19 | *** | −39.0 | .07 | −2.7 | ||
| 100–<200% | .13 | .24 | *** | −27.4 | .14 | −1.1 | ||
| 200–<300% | .18 | .20 | + | −3.8 | .17 | 2.9 | ||
| 300–<400% | .19 | .13 | *** | 16.2 | .19 | −1.2 | ||
| Missing | .10 | .11 | ** | −3.6 | + | .09 | + | 4.5 |
| Parent receiving public assistance | .15 | .32 | *** | −39.7 | .14 | 2.4 | ||
| Social control | 3.90 | 3.95 | * | −4.5 | 3.96 | * | −5.7 | |
| Parent-child closeness scale | −.13 | .02 | *** | −14.8 | −.12 | −.7 | ||
| Parent disappointment for child not graduating college (Very disappointed) |
||||||||
| Somewhat disappointed | .38 | .42 | *** | −9.3 | .38 | .5 | ||
| Not disappointed | .06 | .18 | *** | −37.5 | .06 | .4 | ||
| Household size | 4.41 | 4.60 | *** | −13.2 | 4.41 | −.4 | ||
| Ever repeated grade | .05 | .26 | *** | −60.0 | .05 | .1 | ||
| Ever suspended | .11 | .33 | *** | −57.4 | .10 | .3 | ||
| Ever expelled | .01 | .05 | *** | −27.6 | .01 | −.1 | ||
| Ever truant | .18 | .33 | *** | −34.3 | .19 | −2.5 | ||
| Standardized scale of grades | −.66 | .21 | *** | −98.4 | −.64 | −2.1 | ||
| Vocabulary score | 108.08 | 99.02 | *** | 69.7 | 108.5 | −3.2 | ||
| Disabled | .03 | .03 | −2.2 | .03 | −1.0 | |||
| School integration scale | 1.31 | 1.49 | *** | −27.1 | 1.29 | 2.9 | ||
| Getting along with teachers scale | .67 | .95 | *** | −32.2 | .65 | 1.6 | ||
| Problem with attention scale | 1.15 | 1.28 | *** | −12.7 | 1.15 | .3 | ||
| Problems with homework scale | 1.01 | 1.28 | *** | −26.8 | 1.03 | −1.9 | ||
| Getting along with students scale | .73 | .94 | *** | −22.8 | .72 | 1.1 | ||
| College expectations scale | 4.74 | 3.94 | *** | 85.0 | 4.70 | ** | 4.2 | |
| Desire for college attendance scale | 4.84 | 4.30 | *** | 62.6 | 4.80 | ** | 4.3 | |
| Expectations to live to 35 scale | 4.56 | 4.32 | *** | 30.4 | 4.55 | .9 | ||
| Expectations killed by 21 scale | 1.59 | 1.67 | *** | −10.7 | 1.60 | −.7 | ||
| Protective factors scale | .11 | −.02 | *** | 25.1 | .11 | 1.0 | ||
| Depressive symptoms scale | −.29 | .05 | *** | −36.2 | −.30 | 1.4 | ||
| Ever had sex | .24 | .43 | *** | −39.9 | .24 | 1.2 | ||
| Self-rated health | 4.11 | 3.81 | *** | 35.4 | 4.14 | −3.4 | ||
| How often missed school | .30 | .46 | *** | −27.6 | .28 | 2.6 | ||
| Smoking status (non-smoker) | ||||||||
| Daily smoker | .03 | .11 | *** | −32.4 | .03 | .7 | ||
| Former smoker | .02 | .04 | *** | −8.9 | .02 | .5 | ||
| Infrequent smoker | .04 | .09 | *** | −21.2 | .04 | −1.1 | ||
| BMI | 21.81 | 22.91 | *** | −25.5 | 21.77 | .9 | ||
| Number of close friends that smoke | .45 | .92 | *** | −48.2 | .44 | 1.6 | ||
| Alcohol consumption (nondrinker) | ||||||||
| Usually has one drink | .12 | .10 | * | 4.9 | .11 | 3.3 | ||
| Usually has two drinks | .08 | .08 | 0.1 | .07 | 1.9 | |||
| Usually has 3+ drinks | .23 | .31 | *** | −18.1 | .24 | −1.6 | ||
| Drunk in last year | .45 | .67 | *** | −19.3 | .47 | −1.9 | ||
| Number of close friends that drink | .93 | 1.17 | *** | −21.1 | .94 | −1.0 | ||
| Physical activities in last week | 5.79 | 5.38 | *** | 11.3 | 5.71 | 2.1 | ||
| Visited dentist within last year | .80 | .63 | *** | 37.3 | .80 | .2 | ||
| Vegetable consumption (twice) | ||||||||
| None | .24 | .36 | *** | −26.9 | .24 | .5 | ||
| Once | .42 | .38 | *** | 8.2 | .41 | 1.2 | ||
| Sweet snack consumption (none) | ||||||||
| Once | .36 | .32 | *** | 9.1 | .36 | .6 | ||
| Twice | .23 | .22 | 2.5 | .23 | −.4 | |||
| How often wears seatbelt | 3.41 | 3.00 | *** | 38.2 | 3.40 | .5 | ||
| Usually gets enough sleep | .70 | .73 | ** | −6.3 | .72 | + | −4.4 | |
| Hours of screentime | 19.32 | 24.58 | *** | −25.8 | 19.35 | −.2 | ||
| Delinquent behaviors scale | −.20 | .08 | *** | −31.5 | −.17 | −3.1 | ||
| Religious attendance scale | 1.96 | 1.68 | *** | 24.5 | 1.96 | .6 | ||
| Religious importance scale | 1.33 | 1.26 | *** | 9.7 | 1.29 | * | 5.3 | |
| Neighborhood quality scale | −.16 | −.04 | *** | −13.1 | −.13 | −3.2 | ||
| Average bias | 26.3 | 2.1 | ||||||
***
p < .001;
**
p < .01;
*
p <.05;
+
p>.10
Source: Add Health.
Notes: Significance levels indicate results from t-tests based on regressions of the variables on a treatment indicator. Percentage of covariate bias is defined as the difference of the sample means in the treated and non-treated (full or matched) sub-samples as a percentage of the square root of the average of the sample variances in the treated and non-treated groups (Rosenbaum and Rubin, 1985).