Table 2.
Estimated α and β Parameters Based on the 2-Parameter Item Response Theory Model, Rhode Island, Behavioral Risk Factor Surveillance System, 2004
| Indicatora | Discrimination Parameter: αb Estimate (95% CI) | Difficulty Parameter: βb Estimate (95% CI) |
|---|---|---|
| Poor or fair general health | 1.51 (1.34-1.69) | 2.60 (2.41-2.80) |
| Activity limitationc | 3.18 (2.57-3.80) | 2.97 (2.77-3.17) |
| Physically unhealthyc | 2.21 (1.91-2.50) | 2.65 (2.47-2.84) |
| Pain-related activity limitationc | 1.80 (1.57-2.04) | 2.85 (2.65-3.06) |
| Lack of energyc | 1.20 (1.06-1.33) | 1.86 (1.68-2.04) |
| Mentally unhealthyc | 1.45 (1.25-1.64) | 3.11 (2.86-3.35) |
| Sad, blue, or depressedc | 1.75 (1.50-2.01) | 3.19 (2.95-3.42) |
| Worried, tense, or anxiousc | 1.29 (1.12-1.46) | 2.98 (2.74-3.23) |
| Lack of rest or sleepc | 0.69 (0.59-0.79) | 2.84 (2.52-3.15) |
Abbreviation: CI, confidence interval.
a
Variable descriptions are included in the Methods section and in Jiang et al (1).
b
Significant for all 9 indicators.
c
Respondents reported this indicator for ≥14 days/month.