Table 4.
Difference and correlation between the different simple indicators and the ‘gold standard’ for measuring relative availability of healthy versus unhealthy foods in supermarkets
| Measure | Result | Indicator 1 | Indicator 2 | Indicator 3 | Indicator 4 | Indicator 5 |
|---|---|---|---|---|---|---|
| fresh and frozen fruit and vegetables: soft drinks, crisps, sweet biscuits, cakes and slices, confectionery | fresh fruit and vegetables: soft drinks, energy drinks | fresh fruit and vegetables: soft drinks, crisps, confectionery | fresh and frozen fruit and vegetables: soft drinks, energy drinks, crisps, sweet biscuits, confectionery | frozen fruit and vegetables: soft drinks, energy drinks, crisps and snacks | ||
| Shelf length | Average ratio | 0.28 ± 0.07 | 1.24 ± 0.38 | 0.35 ± 0.10 | 0.29 ± 0.08 | 0.07 ± 0.04 |
| Range (min-max) of ratio | 0.17–0.45 | 0.65–1.88 | 0.18–0.53 | 0.16–0.48 | 0.03-0.19 | |
| Average difference from ‘gold standard’ | 0.057 ± 0.040 | 0.962 ± 0.317 | 0.078 ± 0.074 | 0.053 ± 0.040 | 0.207 ± 0.114 | |
| z-score (Wilcoxon) | -0.057 | -3.408 | -3.010 | -0.795 | -3.408 | |
| p-value (Wilcoxon) | 0.955 | 0.001 | 0.003 | 0.427 | 0.001 | |
| Correlation (spearman) | 0.696 | 0.743 | 0.750 | 0.750 | 0.079 | |
| p-value | 0.004 | 0.002 | 0.001 | 0.001 | 0.781 | |
| Variety (including different sizes) | Average ratio | 0.23 ± 0.03 | 0.85 ± 0.17 | 0.23 ± 0.04 | 0.25 ± 0.03 | 0.19 ± 0.05 |
| Range (min-max) of ratio | 0.17–0.30 | 0.59–1.21 | 0.16–0.31 | 0.18–0.29 | 0.11–0.26 | |
| Average difference from ‘gold standard’ | 0.028 ± 0.0154 | -0.586 ± 0.149 | 0.043 ± 0.016 | 0.020 ± 0.011 | 0.069 ± 0.039 | |
| z-score (Wilcoxon) | -3.181 | -3.408 | -2.385 | -1.874 | -3.351 | |
| p-value (Wilcoxon) | 0.001 | 0.001 | 0.017 | 0.061 | 0.001 | |
| Correlation (spearman) | 0.311 | 0.632 | 0.332 | 0.507 | 0.404 | |
| p-value | 0.260 | 0.011 | 0.226 | 0.054 | 0.136 | |
| Variety (excluding different sizes) | Average ratio | 0.27 ± 0.03 | 1.46 ± 0.39 | 0.28 ± 0.05 | 0.29 ± 0.03 | 0.27 ± 0.05 |
| Range (min-max) of ratio | 0.19–0.34 | 0.77–2.29 | 0.19–0.37 | 0.22–0.34 | 0.18–0.34 | |
| Average difference from ‘gold standard’ | 0.021 ± 0.014 | 1.193 ± 0.361 | 0.039 ± 0.030 | 0.029 ± 0.026 | 0.028 ± 0.030 | |
| z–score (Wilcoxon) | -1.136 | -3.408 | -0.057 | -2.897 | -0.454 | |
| p-value (Wilcoxon) | 0.256 | 0.001 | 0.955 | 0.004 | 0.650 | |
| Correlation (spearman) | 0.557 | 0.754 | 0.318 | 0.564 | 0.686 | |
| p-value | 0.031 | 0.001 | 0.248 | 0.028 | 0.005 |