Table 2.

Differences between smokers and non-smokers in strength of urges to smoke by method of quitting

Method of quitting	n	Mean (SD) strength of urges to smoke in smokers	n	Mean (SD) strength of urges to smoke in non-smokers	Mean difference (95% CI) in strength of urges to smoke
E-cigarettes	371	2.3 (1.1)	93	0.8 (1.1)	1.4 (1.2–1.7)
NRT over-the-counter	1728	2.3 (1.0)	194	1.2 (1.3)	1.2 (1.0–1.3)
No aid	2942	2.0 (1.0)	535	0.7 (1.1)	1.3 (1.2–1.4)

NB: the mean differences are calculated from exact rather than the rounded figures presented in columns 3 and 5 of this table. The mean difference in strength of urges to smoke was not different across the methods of quitting (F_{(2, 5856)} = 1.50, P = 0.22 for the interaction term between smoking status and method of quitting adjusted for the time since the quit attempt started). SD = standard deviation; CI = confidence interval; NRT = nicotine replacement therapy.