Table 1

Stanford trials: comparisons of baseline characteristics

VariableTrial 1
N=224
Trial 2
N=362
Trial 3
N=304
Trial 4
N=243
Trial 5
N=223
Significance*Effect size*Significance†Effect size*
M (SD)M (SD)M (SD)M (SD)M (SD)
Cigarettes per day25.6 (11.5)20.2 (8.2)20.1 (7.4)19.8 (7.1)17.4 (6.6)F(4, 1348)=30.3
p<0.001
0.08esF(4, 1342)=27.9
p<0.001
0.08es
Nicotine dependence‡14.8 (2.5)16.6 (3.5)16.5 (3.7)15.4 (2.9)14.7 (3.0)F(4, 1344)=21.2
p<0.001
0.06esF(4, 1338)=21.0
p<0.001
0.06es
Current depressive symptoms§7.6 (7.6)7.8 (6.6)6.7 (6.8)7.7 (7.8)10.0 (7.7)F(4, 1345)=7.2
p<0.001
0.02esF(4, 1339)=5.6
p<0.001
0.01es
Age46.1 (11.5)45.6 (10.9)45.9 (10.9)44.1 (10.7)43.1 (11.9)F(4, 1348)=3.4
p=0.01
0.01es
Body mass index27.5 (5.0)28.0 (5.3)28.0 (5.7)28.4 (5.5)27.7 (6.0)F(4, 1344)=0.85
p=0.49
0.003es
% Female46.046.140.230.539.9χ2(4)=17.6
p=0.001
0.11v
% Married46.047.249.539.133.2χ2(4)=18.5
p=0.001
0.12v
% Minority12.522.224.326.328.3χ2(4)=19.4
p<0.001
0.12v
% College degree33.027.733.630.533.6χ2(4)=3.8
p=0.43
0.05v
  • *0.01 small, 0.06 medium, 0.14 large; η2: 0.04 recommended minimum effect size; Cramer's V: 0.2 recommended minimum effect size.

  • †Significance after controlling for sex, age, marital/partner status and minority status.

  • ‡Nicotine dependence was self-reported using a modified version of the Fagerström Tolerance Questionaire.33

  • §Current depressive symptoms were self-reported using the Center for Epidemiologic Studies Depression Scale.

  • ¶Partnered refers to participants who reported that they were married.

  • es, η2; v, Cramer's V.