Table 2.
Coefficients (odds-ratios) from the final penalized and un-penalized logistic regression models predicting self-reported sexual assault victimization among women in the selected AAS subsample (2009-2012)a
| Penalized | Unpenalized | |||||
|---|---|---|---|---|---|---|
| % | (se) | OR | OR | (95% CI) | VIFb | |
| I. Prior crime | ||||||
| Administratively-recorded sexual crime victimization (not time-lagged) | 1.5 | (0.3) | 32.0 | 130.9* | (101.2-169.2) | 1.0 |
| Perpetrator of illegal drug possession crime (past 12 months) | 0.1 | (0.1) | 140.4 | 3226.1* | (1102.0-9443.5) | 1.0 |
| II. Clinical factors | ||||||
| Number of outpatient visits (past 12 months) for…c | ||||||
| Traumatic stress | 0.9 | (0.3) | 5.6 | 6.8 | (5.2-8.9) | 1.1 |
| Injury-poisoning | 16.1 | (1.3) | 1.3 | 2.7 | (2.3-3.2) | 1.1 |
| Number of prescriptions (past 12 months) of…c | ||||||
| Benzodiazepines | 5.5 | (1.0) | 1.2 | 1.4 | (1.2-1.6) | 1.1 |
| Other sedatives-hypnotics | 5.6 | (0.8) | 1.3 | 1.6 | (1.4-1.8) | 1.1 |
| Medications to treat migraine | 1.4 | (0.4) | 1.8 | 2.2 | (1.8-2.6) | 1.0 |
| Any prescription for short-acting narcotic analgesic (past 12 months) | 20.0 | (1.5) | 1.1 | 3.5 | (2.8-4.4) | 1.1 |
Abbreviations: OR, odds ratio; 95% CI, 95% confidence interval; VIF, variance inflation factor; PTSD,
All predictors shown here were significant at the .05 level (2-sided test) in univariate models but only two are significant in the unpenalized logistic model. Variable selection in the elastic net model was based on internal cross-validation rather than significance tests, which accounts for why no significance tests are presented for the penalized model ORs and why predictors were included in the final model that were judged to be insignificant based on logistic regression model confidence intervals. The mixing model parameter (α) in the elastic net model was set to 0.9 based on the empirical finding that this was the value that maximized concentration of risk in the 5% of the sample with highest predicted risk. The data were doubly-weighted to adjust for differences in the survey characteristics of AAS respondents who did versus did not agree to have their Army and DoD administrative records linked to their survey responses (Weight 1) and to post-stratify the weighted AAS respondents who agreed to record linkage to match the cross-classification of selected de-identified population-level administrative variables that were provided to us by the Army for this purpose. Confidence intervals in the unpenalized model were calculated using the design-based method of jackknife repeated replications to take these weights into consideration along with the effects of the clustering of observations.
Variance Inflation Factor (VIF) for the coefficient associated with predictor Xi in the above equation equals 1/(1-R2i), where R2i is the coefficient of determination of a regression equation in which Xi is the dependent variable and all the other predictors in the model are included as predictors of Xi. VIF ≥ 5.0 is typically considered an indicator of meaningful multicollinearity.32
These were coded 0-4 (0=0 visits; 1=1-2 visits; 2=3-5 visits; 3=6-10, 4=11+ visits). The value reported in the percentage column reflects the proportion of the sample with one or more visits or prescriptions in the past 12 months.