Table 4

Mean socio-demographic group difference (percentile points) and degree of consistency in socio-demographic differences across practices (indicated by the respective 95% midrange)*

VariableMean difference95% midrange of practice differences (within which ∼95% of practices lie)
Lower limitUpper limit
GenderWomen (vs men)−0.4−2.71.9
Age group18–25 (vs 75–84)
Ethnic groupMixed (vs White)−3.9−16.18.2
South Asian (vs White)−4.3−12.64.0
Black (vs White)−1.4−7.95.0
Chinese (vs White)−8.5−18.31.3
Other (vs White)−4.3−11.83.1
DeprivationDeprivation group 1 (least deprived) vs deprivation group 5 (most deprived))−0.3−3.93.3
Self-rated health status‘Poor’ (vs ‘excellent’)−6.1−12.50.3
Longstanding psychological or emotional condition‘Yes’ (vs ‘no’)0.7−5.46.8
  • * 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