Table 2

Summary of overall intervention effect for price discounts and tailored nutrition education, and any interaction of the intervention effect with social group (ethnicity, household income, educational qualification)

InterventionOutcomeAll participantsp Value for interaction of intervention effect with social group
Difference in means (SE)95% CIEthnicity (Māori, Pacific, European/other)Household income (<NZ$60 000, >NZ$60 000, missing)Educational qualifications (nil/secondary, tertiary/trade/other)
Price discountsSaturated fat (% energy)
 Intervention (6 months)−0.02 (0.19)−0.40 to 0.360.020.380.15
 Follow-up (12 months)−0.12 (0.20)−0.51 to 0.270.300.320.10
All healthier discounted foods purchased (kg/week)
 Intervention (6 months)0.79*** (0.19)0.43 to 1.160.040.980.81
 Follow-up (12 months)0.38* (0.19)0.01 to 0.760.430.480.09
Tailored nutrition educationSaturated fat (% energy)
 Intervention (6 months)−0.09 (0.19)−0.47 to 0.300.690.790.45
 Follow-up (12 months)−0.21 (0.20)−0.60 to 0.180.650.080.04
All healthier discounted foods purchased (kg/week)
 Intervention (6 months)0.07 (0.19)−0.30 to 0.440.200.980.72
 Follow-up (12 months)−0.01 (0.19)−0.39 to 0.370.280.990.46
  • *p<0.05 for intervention effect.

  • ***p<0.001 for intervention effect.

  • Change from baseline with intervention versus change from baseline without intervention calculated by using repeated-measures mixed model regression analysis. The model for the study population as a whole was adjusted for baseline nutrient and food purchases, ethnicity, income, age and sex.

  • Significance of interaction with ethnicity was performed using analysis of covariance regression (ANCOVA) under a similar regression model as described above (excluding ethnicity or income), with separate models for ‘intervention’ and ‘follow-up’ outcomes.