1. A Cox proportional hazards model is estimated relating time to psychiatric hospitalization in patients with severe mental illness. The risk factors include age, sex, prior hospitalization for mental illness, and an indicator of bipolar disorder. The parameter estimates and significance levels for the model are shown here. Which of the predictors are statistically significantly associated with time to psychiatric hospitalization?

Predictor	Parameter Estimate	p-value
Age, years	0.0045	0.5647
Sex (0 = female, 1 = male)	-0.4841	0.0341
Prior hospitalization (0 = no, 1 = yes)	0.3726	0.6178
Bipolar disorder (0 = no, 1 = yes)	0.7561	0.0042

1. Sex & Bipolar disorder
2. Sex & Age
3. Prior hospitalization & Bipolar disorder
4. None of Above