Table 1.

Descriptive statistics by school

School		Jefferson			Sunshine
Wave	1	2	3	1	2	3
Individual
Smoking	.81(.82)	.74(.87)	.86(.90)	.38(.62)	.27(.59)	.34(.65)
Increase (N)		61	99		86	117
Decrease (N)		102	59		173	75
Male	51%			52%
Age	15.73(1.20)			16.09(1.04)
Race
White	92%			5%
Black	4%			22%
Hispanic	3%			40%
Asian	1%			32%
Other	1%			1%
Alcohol	.73(.52)			.60(.58)
GPA	2.59(.77)			2.69(.76)
Self-control	.33(.06)			.33(.05)
Parent smoke	76%			58%
Extracurric. Part.	83%			74%
Network
M degree	5.24	3.95	3.18	2.74	2.01	1.43
SD outdegree	2.78	2.52	2.46	2.65	1.84	1.60
SD indegree	4.05	2.70	2.34	2.58	1.75	1.43
Jaccard Index		.23	.21		.17	.16
Reciprocity	.27	.24	.23	.24	.17	.19
Network and smoking autocorrelation
Geary’s C	.61	.66	.60	.74	.68	.65
Moran’s I	.34	.31	.34	.19	.19	.24
Avg. Similarity	.81	.74	.86	.38	.27	.34
N	757	617	479	1673	1249	850

Note: Mean indegree (number of incoming ties) equals mean outdegree (number of outgoing ties) by definition. Geary’s C ranges from 0 to 2, with lower values indicating stronger positive correlation between friends’ smoking. Moran’s I ranges from −1 to +1, with higher values indicating stronger positive correlation between friends’ smoking. For both measures, the midpoint of the range indicates no correlation between friends’ smoking.