Table 3.
Differential item functioning for executive function items related to age, education, gender, and ethnicity/language group*
| Age | Education | Gender | Ethnicity/language | |||||
|---|---|---|---|---|---|---|---|---|
| Item | U | NU | U | NU | U | NU | U | NU |
| Animals 1 | 2% | 0.19 | 6% | 0.67 | 0% | 0.31 | 7% | 0.55 |
| Animals 2 | 2% | 0.19 | 15% | 0.2 | 0% | 0.66 | 15% | 0.03 |
| F 1 | 2% | 0.96 | 2% | 0.21 | 0% | 0.43 | 1% | 0.05 |
| F 2 | 1% | 0.44 | 3% | 0.32 | 0% | 0.01 | 2% | 0.65 |
| L 1 | 0% | 0.25 | 1% | 0.64 | 0% | 0.84 | 0% | 0.4 |
| L 2 | 0% | 0.86 | 3% | 0.33 | 0% | 0.34 | 1% | 0.03 |
| Supermarket Items 1 | 1% | 0.14 | 11% | 0.24 | 0% | 0.41 | 6% | 0.03 |
| Supermarket Items 2 | 2% | <0.01 | 2% | 0.22 | 0% | 0.13 | 0% | 0.79 |
| Supermarket Categories | 2% | <0.01 | 2% | 0.39 | 1% | 0.86 | 5% | 0.19 |
| Digit Span Backward | 3% | 0.09 | 16% | <0.01 | 0% | 0.08 | 10% | 0.91 |
| Visual Span Backward | 1% | <0.01 | 18% | 0.64 | 1% | 0.35 | 12% | 0.04 |
| List Sorting 1 | 0% | <0.01 | 10% | 0.11 | 0% | 0.12 | 5% | 0.84 |
| List Sorting 2 | 1% | 0.43 | 9% | 0.13 | 0% | 0.24 | 4% | 0.49 |
Numbers in the “U” columns represent uniform DIF findings. Uniform DIF occurs in an item if members of one group are at a consistent advantage or disadvantage for that item relative to another group for every executive function level. For example, people with lower levels of educational attainment had lower expected scores on the animals item compared to people with higher educational attainment at all levels of executive function. The numbers shown here represent the proportional change in the β1 coefficient from including or excluding the group term or terms from models 2 and 3. Changes with an absolute value of at least 7% are shown in bold font. Larger values indicate larger differences in expected score across groups for a given executive function level. Numbers in the “NU” columns represent non-uniform DIF findings. Non-uniform DIF occurs in an item if there is an interaction between executive function level, group membership, and expected scores. For example, this occurred for the supermarket categories item related to age. There are two possible relationships when there is nonuniform DIF. First, the probabilities may cross, so that older people have (for example) a higher expected score at high executive function levels, but lower expected scores at lower executive function levels. Second, the probabilities may not cross, but be more extreme at one end of the executive function spectrum than the other, so that older people have (for example) a lower expected score at high executive function levels, but much lower expected scores at low executive function levels. The numbers shown here are p values associated with the likelihood difference between models 1 and 2 (including or excluding the interaction term or terms). P values less than 0.05 are shown in bold font. Here smaller values indicate more statistically significant interaction between the group term and overall executive function. See Appendix 3 for details.