Table 8.
Multiple regression: effect of each factor on TCI total score.
| Predictor (reference category) | Test of predictor‡ | Fixed components | Random components | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| δ | d.f. | P | Parameter | Estimate | 95% CI | p | Parameter | σ | 95% CI | |
| Gender | 4.34 | 1 | 0.036 | constant | 54.49 | 49.33, 59.65 | <0.001 | Practices | 1.29 | 0.02, 2.57 |
| male | 3.66 | 0.23, 7.08 | 0.04 | Individuals | 7.93 | 7.22, 8.64 | ||||
| Tenure | 3.85 | 1 | 0.049 | tenure/year | 0.13 | 0.00, 0.26 | 0.05 | |||
| Professional groups (GP) | 7.57 | 4 | 0.109 | nurse | -5.36 | -9.31, -1.40 | 0.01 | |||
| admin | -3.42 | -6.75, -0.08 | 0.04 | |||||||
| com nurse | -3.21 | -7.56, 1.16 | 0.15 | |||||||
| Other | -1.60 | -5.48, 2.28 | 0.41 | |||||||
| Practice list size (≤ 3500) | 5.20 | 2 | 0.074 | 3501–7000 | -4.07 | -7.43, -0.72 | 0.02 | |||
| >7000 | -3.15 | -6.84, 0.54 | 0.09 | |||||||
| Number of GPs (1 or 2) | 7.28 | 2 | 0.026 | 3–5 | -2.53 | -7.18, 2.13 | 0.29† | |||
| 6 or more | 1.79 | -3.24, 6.82 | 0.49† | |||||||
‡ The relative importance of each predictor is assessed by comparing the change in -2 log-likelihood that occurs when a particular predictor is omitted from the final model with the percentage points of a chi-squared distribution with degrees of freedom given in the column titled d.f.
σ = standard deviation of TCI scores (either between practices or between individuals within practices as specified).
† These estimates suggest that the difference between the smallest practice and the medium size practices and the difference between the smallest practices and the largest practices are not statistically significant; however the difference between medium and large practices is 4.32 with 95% CI (1.37, 7.28).