Table 2 Strategies used to evaluate the validity of the sustainable diet index-US (SDI-US)
Question | Strategy | Output |
|---|---|---|
Content validity | ||
1. Does the index capture the key dimensions of sustainable diets defined by the Food and Agriculture Organization? | Followed and checked the relevance of each indicator based on the original SDI development study (Seconda et al., Br J Nutr 2019;121:1166-77) | Table 1 |
2. Does a single individual indicator have an oversized impact on the total score? | Estimated Pearson correlations between the individual indicators and the total SDI-US | Table 3 |
3. Does one sub-index have an oversized impact on the total score? | Estimated Pearson correlations between the sub-indices and the total SDI-US and between the index after removing each sub-index and the total SDI-US | Table 3 |
Construct validity | ||
4. Does the index differentiate between groups with known differences in diet quality? i.e., does it have concurrent-criterion validity? | Applied general linear models to compare male and female, older and younger adults, different race/Hispanic origins, and different education level groups | Table 4 |
5. Does the index correctly measure what it should measure (sustainability of diets)? e.g., does plant-based foods consumption increase as the SDI-US score increases? | Evaluated the association between the SDI-US and the consumption of selected food groups included in the DGA, the alternative Mediterranean diet score, and the EAT-Lancet diet score | Table 5 |