Table 1.
Design adjusted symptom endorsement rates and item response parameter estimates
| Number (%) endorsing each symptom |
|||||
| Symptom | Nondaily | Daily | Discrimination (slope) | Severity (threshold) | Δχ2 p value |
| Spent great deal of time getting, using, or getting over effects of cigarettes | 752 (32.2) | 297 (66.45) | 1.24 | 0.81 | .668 |
| Used cigarettes more often or in larger amounts than intended | 608 (27.3) | 266 (58.3) | 1.67 | 0.96 | NA |
| Built up a tolerance so that same amount of cigarettes had less effect than before | 587 (25.8) | 247 (56.7) | 1.31 | 1.03 | 0.928 |
| Cigarette use kept you from working, going to school, taking care of children, or engaging in recreational activities | 186 (6.5) | 51 (11.8) | 1.17 | 2.10 | .038 |
| Cigarette use caused emotional or psychological problems | 176 (7.0) | 29 (6.6) | 1.24 | 2.13 | .028 |
| Cigarette use caused health problems | 201 (8.5) | 92 (21.3) | 1.03 | 2.25 | .247 |
| Wanted or tried to stop or cut down on your cigarette use | 736 (33.2) | 263 (58.4) | 0.85 | 0.82 | .301 |
Note. Item response estimates are from the final IRT model in which the severity and discrimination parameters were constrained to be equal across nondaily and daily smoking groups. The Δχ2 p value represents the p value for the change in chi-square between the model in which the discrimination and severity parameters were free to vary across groups (baseline model) and the model in which these parameters for the symptom of interest were constrained to be equal across groups. The Benjamini–Hochberg correction for multiple significance tests was used for all significance tests. NA = anchor item initially constrained to be equal across groups for model identification.