Table 1.

Results of meta-analyses of trials of nicotine gum to reduce smoking using standard and 'treat-as-one-trial' methods, with risk difference as effect measure

	Pooled risk difference (95% CI)	P	NNT
(a) Two selected trials (see text)
Standard meta-analysis (Mantel-Haenszel method)	0.060 (0.025 to 0.095)	0.001	16.7
Treat-as-one-trial	0.033 (0.001 to 0.064)	0.04	30.7
(b) All 51 trials
Standard meta-analysis (Mantel-Haenszel method)	0.061 (0.050 to 0.071)	<0.001	16.4
Treat-as-one-trial	0.081 (0.070 to 0.092)	<0.001	12.3