Table 3

Estimates of effect of price discounts (n=513) versus no price discounts (n=515) on mean change from baseline in nutrient and food purchases by ethnicity

MāoriPacificEuropean/otherAll participantsInteraction with ethnicity
Difference in means (SE)95% CIDifference in means (SE)95% CIDifference in means (SE)95% CIDifference in means (SE)95% CIp Value
Saturated fat (% energy)
 Intervention (6 months)0.35 (0.52)−0.68 to 1.391.09 (0.74)−0.38 to 2.56−0.34 (0.21)−0.75 to 0.06−0.02 (0.19)−0.40 to 0.360.02
 Follow-up (12 months)−0.48 (0.57)−1.60 to 0.65−1.04 (0.81)−2.64 to 0.55−0.06 (0.21)−0.47 to 0.36−0.12 (0.20)−0.51 to 0.270.30
 Food purchases (kg/week)
All foods
  Intervention (6 months)−0.13 (0.94)−1.98 to 1.711.51 (1.16)−0.78 to 3.801.13** (0.32)0.50 to 1.760.90* (0.31)0.29 to 1.520.24
  Follow-up (12 months)−0.19 (0.99)−2.14 to 1.752.40 (1.25)−0.06 to 4.870.34 (0.32)−0.29 to 0.980.37 (0.32)−0.26 to 1.000.24
All healthier discounted foods
  Intervention (6 months)−0.15 (0.48)−1.10 to 0.801.20* (0.57)0.06 to 2.341.02** (0.21)0.60 to 1.430.79** (0.19)0.43 to 1.160.04
  Follow-up (12 months)−0.12 (0.51)−1.13 to 0.891.07 (0.62)−0.15 to 2.290.47* (0.21)0.05 to 0.890.38* (0.19)0.01 to 0.760.43
Healthier discounted fruit and vegetables
  Intervention (6 months)−0.05 (0.37)−0.78 to 0.670.86* (0.42)0.03 to 1.690.59** (0.16)0.28 to 0.890.48** (0.14)0.21 to 0.750.13
  Follow-up (12 months)0.01 (0.39)−0.75 to 0.780.65 (0.46)−0.25 to 1.560.33* (0.16)0.02 to 0.640.28* (0.14)0.00 to 0.560.63
  • *p<0.05 for intervention effect.

  • **p<0.01 for interaction between intervention and period.

  • ***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), with separate models for ‘intervention’ and ‘follow-up’ outcomes.