Estimated percentage change in quit attempts (the proportion of smokers who attempted to quit in the past 2 months) per 10% change in mass media expenditure from ARIMAX models
| Quit attempts | Unadjusted | Adjusted for covariates in table |
| Percentage change per 10% change in the exposure (95% CI), p Value | Percentage change per 10% change in the exposure (95% CI), p Value | |
| Model 1 | ||
| Mass media expenditure (lag 0) | −0.04 (-0.63 to 0.54), 0.883 | −0.03 (-0.62 to 0.56), 0.931 |
| Weekly spend tobacco (lag 4) | −0.51 (-2.89 to 1.87), 0.677 | |
| Tobacco control policies | 0.06 (-0.49;0.62), 0.830 | |
| Best fitting model | ARIMAX (0, 1, 1) (0, 0, 0) | ARIMAX (0, 1, 1) (0, 0, 0) |
| Non-seasonal (p)—AR | NA | NA |
| —MA | <0.001 | <0.001 |
| Seasonal (p)—AR | NA | NA |
| —MA | NA | NA |
| R2 | 0.010 | 0.012 |
| Model 2 | ||
| Mass media expenditure (lag 2) | −0.05 (-0.67 to 0.56), 0.861 | −0.03 (-2.05 to 2.00), 0.979 |
| Weekly spend tobacco (lag 4) | −0.51 (-2.94 to 1.93), 0.684 | |
| Tobacco control policies | −0.06 (-0.50 to 0.62), 0.831 | |
| Best fitting model | ARIMAX (0, 1, 1) (0, 0, 0) | ARIMAX (0, 1, 1) (0, 0, 0) |
| Non-seasonal (p)—AR | NA | NA |
| —MA | <0.001 | <0.001 |
| Seasonal (p)—AR | NA | NA |
| —MA | NA | NA |
| R2 | 0.010 | 0.012 |
The assumption of normally distributed errors was met. When the lag for weekly tobacco spend was set to zero, results for mass media were similar in model 1 (β=−0.04 (–0.63 to 0.54) , p=0.882) or in model 2 (β=−0.05 (-0.66; to 0.56), p=0.864). Addition of MA or AR terms did not improve the models.
AR, autoregressive terms; ARIMAX, Autoregressive integrated moving average modelling with exogenous variables;MA, moving average terms.