Table 4. Quitting behaviour and outcomes.

	Intervention (%)	Comparison (%)	p Value
Responder estimates
Attempted to quit (ni = 918; nc = 345)	83.8	74.8	⩽0.001
Quit at 3 months (ni = 863; nc = 329)	46.0	29.5	⩽0.001
Quit at 6 months (ni = 832; nc = 305)	37.1	26.2	⩽0.001
Quit at 12 months (ni = 672; nc = 257)	33.2	28.0	NS
Period prevalence (sustained quitting from 3-month to 6-month follow-ups) (ni = 861; nc = 329)	20.7	13.1	⩽0.01
Period prevalence (sustained quitting from 3-month to 12-month follow-ups) (ni = 748; nc = 303)	2.7	2.0	NS
Conservative estimates
Attempted to quit (conservative estimate: ni = 1000; nc = 377)	76.9	68.4	⩽0.001
Quit at 3 months (ni = 1000; nc = 377)	39.7	25.7	⩽0.001
Quit at 6 months (ni = 1000; nc = 377)	30.9	21.2	⩽0.001
Quit at 12 months (ni = 1000; nc = 377)	22.3	19.1	NS
Period prevalence 3–6 months (ni = 1000; nc = 377)	2.0	1.6	NS
Period prevalence 3–12 months (ni = 1000; nc = 377)	2.0	1.6	NS

n_i, number in sample (that is, denominator) for intervention group; n_c, number in sample for comparison group.