Table 3. Associations between smartphone and self-reported measures of tie strength in a population of 737 young adults.

	Total population	High face-to-face contact frequency (summary score = 20–24)		High non-face-to-face contact frequency (summary score = 20–24)
Smartphone measures per month	N (%)	OR	95%CI	OR	95%CI
Frequency of call interactions per alter
0–3 calls	221 (30.0)	1	(Ref)	1	(Ref)
4–6 calls	380 (51.6)	2.85	(1.13;7.16)	2.36	(1.34;4.16)
7–9 calls	96 (13.0)	2.51	(0.77;8.22)	3.10	(1.54;6.28)
More than 9 calls	40 (5.4)	6.53	(1.98;21.47)	5.82	(2.55;13.28)
P-value (test for trend)		0.004		<0.0001
Frequency of text interactions per alter
0–14 texts	298 (40.4)	1	(Ref)	1	(Ref)
15–29 texts	240 (32.6)	5.92	(1.94;18.10)	1.80	(1.09;2.98)
30–44 texts	100 (13.6)	5.48	(1.57;19.15)	2.01	(1.08;3.74)
More than 45 texts	99 (13.4)	11.44	(3.63;36.04)	1.58	(0.83;3.02)
P-value (test for trend)		<0.0001		0.072
Call duration
up to 1 hr	160 (21.7)	1	(Ref)	1	(Ref)
1–2 hrs	150 (20.4)	2.43	(0.89;6.66)	1.86	(0.92;3.75)
2–3 hrs	140 (19.0)	2.86	(0.98;8.34)	1.86	(0.90;3.85)
More than 3 hrs	287 (38.9)	3.02	(1.17;7.77)	2.84	(1.51;5.35)
P-value (test for trend)		0.029		0.001
Call reciprocity*
0–3 reciprocated ties	145 (19.9)	1	(Ref)	1	(Ref)
4–6 reciprocated ties	245 (33.7)	1.31	(0.50;3.39)	1.44	(0.72;2.88)
7–9 reciprocated ties	167 (22.9)	2.60	(0.98;6.90)	2.61	(1.30;5.26)
More than 9	171 (23.5)	2.04	(0.73;5.74)	3.47	(1.74;6.93)
P-value (test for trend)		0.069		<0.0001
Text reciprocity
0–6 reciprocated ties	82 (11.1)	1	(Ref)	1	(Ref)
7–12 reciprocated ties	205 (27.8)	2.23	(0.61;8.12)	1.72	(0.75;3.92)
13–18 reciprocated ties	209 (28.4)	1.89	(0.50;7.13)	1.56	(0.67;3.59)
More than 18	241 (32.7)	4.09	(1.09;15.31)	2.23	(0.98;5.08)
P-value (test for trend)		0.040		0.079

OR = Odds ratio, 95%CI = 95% confidence interval. All OR adjusted for age, gender, and co-habitation.

*9 observations excluded because of no calling activity.