Table 3.
Model selection: tobacco outlet density effects
| Maximally parsimonious base models identified via hierarchical fit selection | |||||||
|---|---|---|---|---|---|---|---|
| Parameter 1 | Parameter 2 | Parameter 3 | LL | df | Δ df | G2 | p Value* |
| Density×NDS | Quit×intend | – | −3590.074 | 11 | 21 | 1246.23 | 0.0983 |
| Density×NDS | Quit×intend | Quit×price | −3707.986 | 13 | 51 | 1248.33 | 0.0818 |
| Density×NDS | Quit×intend | Quit×shop around | −3680.451 | 13 | 51 | 1259.84 | 0.0547 |
| Density×NDS | Quit×intend | Quit×brand | −3561.262 | 13 | 51 | 1087.99 | 0.9746 |
| Density×NDS | Quit×intend | Quit×buy all | −3521.556 | 13 | 51 | 1020.09 | 0.9997 |
| Three-way interaction terms yielding the greatest improvement in model fit | |||||||
| Three-way interaction removed from model | LL | df | Δ df | G2 | p Value† | ||
| Density×NDS×price | −3147.028 | 45 | 3 | 43.878 | 0.000 | ||
| Density×NDS×shop around | −3164.394 | 45 | 3 | 59.282 | 0.000 | ||
| Density×NDS×brand | −3132.865 | 45 | 3 | 64.782 | 0.000 | ||
| Density×NDS×buy all | −3070.696 | 45 | 3 | 0.490 | 0.921 | ||
| Density×quit×price | −3133.276 | 45 | 3 | 16.373 | 0.001 | ||
| Density×quit×shop around | −3141.393 | 45 | 3 | 13.281 | 0.004 | ||
| Density×quit×brand | −3108.847 | 45 | 3 | 16.746 | 0.001 | ||
| Density×quit×buy all | −3107.083 | 45 | 3 | 73.264 | 0.000 | ||
| Density×intend×price | −3158.125 | 45 | 3 | 66.072 | 0.000 | ||
| Density×intend×shop around | −3177.342 | 45 | 3 | 85.178 | 0.000 | ||
| Density×intend×brand | −3153.142 | 45 | 3 | 105.335 | 0.000 | ||
| Density×intend×buy all | −3098.246 | 45 | 3 | 55.591 | 0.000 | ||
Price; shop around; brand; buy all: purchase preferences. NDS (converted vs native).
G2: likelihood-ratio test statistic.
*Non-significant deviance from the saturated model.
†Significant increase in deviance on removal of each three-way interaction term.
Intend, intention to attempt cessation within 6 months; LL, log likelihood; NDS, non-daily smoking status; quit, failed quit attempt in previous year.