Table 3.

Mean Differences in Developmental Antecedents by Trajectory Classes of Number of Sexual Partners from Age 16 to Age 22¹

	Class 1 (Zero–Initial) N = 347 (65.8%)	Class 2 (One–Initial) N = 78 (14.8%)	Class 3 (Multiple-Initial) N = 102 (19.4%)
Growth parameters
Intercept	.002 (.002)	1.010 (.009)^***	2.408 (.052)^***
Slope	.325 (.023)^***	.211 (.054)^***	−.428 (.050)^***
Quadratic	−.022 (.004)^***	−.025 (.010)^**	.051 (.009)^***

	M (SD)	M (SD)	M (SD)	F
Number of Sexual Partners at Age 16
	0 (.00)^a	1.00 (.00)^b	2.40 (.49)^c	4226.24^***
Family and Child Characteristics
1. Child gender²	.48 (.50)	.62 (.49)	.46 (.50)	2.64
2. Race³	.12 (.32)^a	.22 (.42)^b	.26 (.44)^b	7.93^***
3. SES	40.72 (12.46)^a	35.94 (13.39)^b	36.05 (13.95)^b	6.83^**
4. Pubertal development	2.56 (.63)^a	2.77 (.66)^b	2.73 (.62)^b	4.51^*
5. Child IQ	100.01 (16.30)^a	96.31 (15.70)	94.35 (13.75)^b	4.80^**
Parent and Peer Relationships
6. Deviant peers	1.32 (.30)^a	1.43 (.47)^b	1.56 (.46)^c	13.88^***
7. Permissiveness	1.56 (.38)	1.65 (.38)	1.65 (.47)	2.36
8. Psychological control	1.39 (.32)^a	1.44 (.26)	1.53 (.44)^b	5.11^**
9. Monitoring knowledge	2.57 (.35)^a	2.52 (.32)^a	2.35 (.45)^b	11.37^***
Adolescent Behavior
10. Internalizing problems	11.40 (7.08)	10.92 (7.72)	12.19 (7.44)	.56
11. Externalizing problems	5.01 (7.60)^a	7.74 (13.08)^b	10.40 (11.47)^b	10.97^***
12. GPA	9.75 (2.75)^a	9.07 (3.07)^a	7.98 (3.20)^b	11.18^***

Note. Means designated with the same superscript are not significantly different based on LSD post-hoc comparisons (p< .05).

At ages 16–18 and 21–22, number of sexual partners was measured as 0 = none, 1 = 1 partner, 2 = 2 to 3 partners, and 3 = more than 3 partners in last 12 months; at age 20, number of sexual partners was measured as 0 = none, 1 = 1 to 2 partners, 2 = 3 to 6 partners, and 3 = more than 6 partners in last 24 months.

Child gender is coded as male = 0 and female = 1.

Race is coded as non-African American = 0 and African American = 1.

p< .05,

^**

p< .01,

^***

p< .001.