Hahn 2005.

Methods	Country: USA Setting: Bluegrass Kentucky 2001 Q&W contest, Lexington‐Fayette county Design: Two‐group quasi‐randomized study
Participants	1006 adults (age 18+) who had used tobacco within the last 30 days. 1. Intervention: 494 volunteer registrants in a Q&W contest (56% of all entrants); average age 38, 68% female, 47% married, 89% white, 65% college education, 48% earning > US$25,000, 98% smoked cigarettes. 2. Control: 512 current smokers selected by random digit dialling from outside the contest area (8.5% of contacted households). average age 42.8, years, 56% female, 54% married, 91% white. 37% college education, 39% earning > US$25,000, 92% smoked cigarettes.
Interventions	Intervention: community quit date; weekly gender‐specific cessation information by post throughout contest; online quit assistance; toll‐free phone quit assistance; media campaign; support through worksites, physicians, health professionals, community leaders. Registrants declared tobacco status, and nominated a tobacco‐free ‘buddy'. Lottery draw for cash prizes (grand prize US$2500 and 5 prizes of US$500) for all validated quitters. Control: baseline and follow‐up surveys only.
Outcomes	7‐day PP. Abstinence at contest end validated by ‘buddy' testimony. Follow‐up telephone interviews at 3 months, 6 months and 12 months, with urinary cotinine test for all quitters at all follow‐up points. Predictors of quitting.
Notes	In the 2005 version of our review, this trial reported on low‐income smokers only. The current version reports full trial data. ITT analysis, with missing or non‐negative urines and dropouts counted as continuing smokers. Originally in Q&W.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Intervention group were all entrants to the Q&W contest; controls were selected by random telephone dialling. Therefore, a sequence was not generated and the intervention group were self‐selected. Treatment group participants were significantly younger than those in the control group, the percentage of females was significantly greater. Nearly two‐thirds of the treatment group had at least some college education, while nearly the same percentage of the control group had at most a high school education. A significantly lower percentage of the control group had household incomes of US$25,000 or more and a higher percentage of treatment group participants smoked cigarettes at baseline than those in the control group. Compared to the control group, significantly fewer members of the treatment group used smokeless tobacco. 70% of the treatment group were at the preparation stage of change or higher, compared with only 16% of those in the control group.
Allocation concealment (selection bias)	High risk	Intervention group were all entrants to the Q&W contest; controls were selected by random telephone dialling. Therefore, the intervention group were self‐selected.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Abstinence was biochemically validated so judged to be at low risk of differential misreport.
Incomplete outcome data (attrition bias) All outcomes	Low risk	In the treatment group, the retention at 3, 6 and 12 months was 85%, 75% and 63%, respectively.The retention rate for the control group at 3, 6 and 12 months was 78%, 66% and 60%, respectively. The dropout rate was judged to not differ significantly between groups.
Other bias	Unclear risk	The following was noted and may have affected the results of the study: Quote: “The findings of this study show that smokers in the control group who were in preparation may have been prompted to quit merely because they were repeatedly interviewed about their tobacco use.”