Skip to main content

Table 2 Sample sizes with different treatment effects and control group quit rates using conservative 'p' value (0.025)

From: Protocol for the Proactive Or Reactive Telephone Smoking CeSsation Support (PORTSSS) trial

Control (reactive support, no offer of NRT) group quit rate at 6 months (%)

Comparison "group" quit rate at 6 months (%)

Intervention "group" quit rate at 6 months (%)

Odds ratio for each treatment effect (proactive vs reactive, NRT vs no NRT)

Power

Required sample size per group (total for 4 groups)

12%*

14%

18.6%

1.4

80%

644 (2576)

12%*

14.5%

20.3%

1.5

80%

426 (1704)

12%

14.5%

20.3%

1.5

90%

550 (2200)

8%**

9.5%

12.8%

1.4

80%

888 (3552)

8%**

10%

14%

1.5

80%

587 (2348)

8%**

10%

14%

1.5

90%

760 (3040)

  1. * self report quit rates, ** biochemically validated quit rates
  2. Final row figures (bold) show our most likely estimates for required sample sizes.