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. Author manuscript; available in PMC: 2020 Aug 30.
Published in final edited form as: J Health Soc Behav. 2019 Sep;60(3):362–376. doi: 10.1177/0022146519870521

Table 2.

Descriptive Statistics of the School Friendship Networks.

School 1 (n = 449) School 2 (n = 288) School 3 (n = 371) School 4 (n = 317)
Characteristics W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4
M friends nominated 5.68 4.89 3.45 2.26 4.30 3.99 5.31 3.93 5.48 5.61 5.59 3.18 6.39 6.12 5.19 2.21
Range friend outdegreea 0–19 0–18 0–16 0–17 0–18 0–19 0–19 0–19 0–19 0–19 0–19 0–18 0–18 0–18 0–17 0–10
Range friend indegreeb 0–22 0–17 0–16 0–10 0–18 0–16 0–20 0–17 0–19 0–16 0–18 0–12 0–23 0–17 0–16 0–12
Reciprocity index .36 .33 .34 .36 .34 .34 .41 .41 .36 .35 .38 .41 .34 .32 .39 .49
Transitivity indexc .17 .15 .16 .15 .17 .19 .21 .25 .18 .18 .18 .22 .16 .16 .17 .2
Moran’s i smokingd .17 .13 .17 .21 .09 .10 .10 .10 .19 .18 .30 .22 .08 .04 .13 .27
P1 P2 P3 P1 P2 P3 P1 P2 P3 P1 P2 P3
% Stable friend ties 26.9 18.7 18.9 3.2 25.1 25.8 32.5 27.0 25.5 26.4 2.7 18.4
% New friend ties 31.7 43.8 26.0 33.0 52.8 27.2 35.8 38.5 22.0 37.2 42.2 25.1
% Friend ties dissolved 41.4 37.5 55.1 36.7 22.2 47.0 31.8 34.5 52.5 36.4 37.1 56.5
Actors joining 0 31 0 0 38 0 0 27 0 0 25 0
Actors leaving 0 80 106 0 21 64 0 23 85 0 41 105
Jaccard coefficiente .27 .19 .19 .30 .25 .26 .33 .27 .26 .26 .21 .18

Note: Survey data were collected from four high schools in one Los Angeles neighborhood from 2010 to 2013. M = mean; W = Wave, P = time period between two consecutive study waves.

a

Outdegree is the number of friend nominations made by a student.

b

Indegree is the number of friend nominations received by a student.

c

Transitivity index represents the proportion of friendship two paths (where A nominates B as a friend and B nominates C) that formed friendship triads (where there are friendship ties between A, B, and C).

d

Moran’s i is a measure of spatial correlation where coefficient values close to 0 indicate that connected individuals (i.e., friends) are not more similar on smoking than would be expected if they were randomly paired and values close to 1 indicate that connected individuals are very similar.

e

The Jaccard index measures the amount of change between consecutive waves and is used to express quantitatively whether the data collection points are not too far apart. Values of .2 to .3 and greater are desired to meet assumptions that the network change process is gradual (Snijders et al. 2010).