Mean socio-demographic group difference (percentile points) and degree of consistency in socio-demographic differences across practices (indicated by the respective 95% midrange)*
| Variable | Mean difference | 95% midrange of practice differences (within which ∼95% of practices lie)† | ||
| Lower limit | Upper limit | |||
| Gender | Women (vs men) | −0.4 | −2.7 | 1.9 |
| Age group‡ | 18–25 (vs 75–84) | 4.6 | 4.6 | 4.6 |
| Ethnic group‡ | Mixed (vs White) | −3.9 | −16.1 | 8.2 |
| South Asian (vs White) | −4.3 | −12.6 | 4.0 | |
| Black (vs White) | −1.4 | −7.9 | 5.0 | |
| Chinese (vs White) | −8.5 | −18.3 | 1.3 | |
| Other (vs White) | −4.3 | −11.8 | 3.1 | |
| Deprivation‡ | Deprivation group 1 (least deprived) vs deprivation group 5 (most deprived)) | −0.3 | −3.9 | 3.3 |
| Self-rated health status‡ | ‘Poor’ (vs ‘excellent’) | −6.1 | −12.5 | 0.3 |
| Longstanding psychological or emotional condition | ‘Yes’ (vs ‘no’) | 0.7 | −5.4 | 6.8 |
* All interaction variance components were significant at <0.0001.
† The squared root of the coefficient for the interaction term variables (case mix adjuster by practice) represents the practice-level SD of the mean practice-level differences associated with the respective variable category or unit. Using normal approximation, the mean difference ±1.96 practice-level SDs represents the 95% midrange intervals of practice-level demographic coefficients.
‡ To improve the accuracy of the interaction variance components in these models, age, self-rated health, and deprivation groups were treated linearly (as opposed to categorically); in addition, the abbreviated six-group (as opposed to 16-group) categorisation of ethnicity was used.24