Table 2.
Item functioning statistics for the applicant group as a whole (n = 547) and differential item functioning assessed for gender, pu-GPA and age
| Mean score% (SD) | Guessing parametera | Slipping parameterb | Item-total correlation | Genderc t (p value) |
pu-GPAd F (p value) |
Agee F (p value) |
|
|---|---|---|---|---|---|---|---|
| V-SJT | |||||||
| 1 | 64.06 (17.80) | 0.30 | 0.99 | 0.04 | 2.02 (0.04)* | 2.26 (0.13) | 0.00 (0.98) |
| 2 | 62.01 (20.46) | 0.28 | 0.22 | 0.22 | 2.66 (0.01)** | 2.11 (0.15) | 0.19 (0.66) |
| 3 | 60.46 (14.52) | 0.19 | 0.00 | 0.21 | − 0.68 (0.50) | 4.24 (0.04)* | 2.41 (0.12) |
| 4 | 72.30 (19.80) | 0.44 | 0.00 | 0.17 | 1.35 (0.18) | 3.03 (0.08) | 0.79 (0.38) |
| 5 | 68.34 (20.68) | 0.00 | 0.00 | 0.15 | 1.96 (0.05) | 1.35 (0.25) | 0.59 (0.44) |
| 6 | 75.88 (18.30) | 0.00 | 0.18 | 0.23 | 1.14 (0.25) | 10.09 (0.00)** | 7.52 (0.01)** |
| 7 | 41.97 (19.46) | 0.05 | 0.00 | 0.36 | 1.46 (0.15) | 0.05 (0.83) | 1.32 (0.25) |
| 8 | 41.43 (23.48) | 0.03 | 0.00 | 0.44 | 1.01 (0.32) | 0.11 (0.74) | 0.54 (0.46) |
| 9 | 42.48 (30.91) | 0.00 | 0.03 | 0.59 | 0.16 (0.87) | 0.78 (0.38) | 0.02 (0.90) |
| 10 | 29.43 (29.85) | 0.05 | 0.00 | 0.43 | 0.98 (0.33) | 0.55 (0.46) | 0.41 (0.52) |
| 11 | 14.88 (23.08) | 0.01 | 0.00 | 0.45 | 0.72 (0.47) | 0.43 (0.52) | 0.38 (0.54) |
| Written Aptitude Test | |||||||
| 1 | 48.74 (21.23) | 0.38 | 0.44 | 0.21 | − 2.81 (0.01)** | 1.34 (0.25) | 1.05 (0.31) |
| 2 | 44.66 (13.77) | 0.42 | 0.36 | 0.20 | − 0.33 (0.74) | 0.93 (0.34) | 10.54 (0.00)** |
| 3 | 61.29 (15.42) | 0.01 | 0.04 | 0.21 | 1.01 (0.31) | 0.95 (0.33) | 0.43 (0.51) |
| 4 | 35.66 (30.07) | 0.07 | 0.12 | 0.25 | − 3.05 (0.00)** | 3.97 (0.05)* | 0.36 (0.55) |
| 5 | 40.35 (30.85) | 0.26 | 0.55 | 0.17 | − 1.29 (0.20) | 2.31 (0.13) | 0.42 (0.52) |
| 6 | 43.48 (16.44) | 0.20 | 0.38 | 0.20 | 0.62 (0.54) | 5.63 (0.02)* | 2.60 (0.11) |
| 7 | 41.97 (19.46) | 0.67 | 0.00 | 0.25 | 0.06 (0.95) | 11.04 (0.00)** | 0.28 (0.60) |
| 8 | 41.43 (23.48) | 0.02 | 0.01 | 0.21 | 0.78 (0.44) | 5.64 (0.02)* | 0.74 (0.39) |
*Significant at p < 0.05
**Significant at p < 0.01
aGuessing is the probability that a respondent responds correctly to the item although he or she has not mastered all the required attributes; analyzed using the G-DINA model with 0 is low and 1 is high
bSlipping is the probability that a respondent responds incorrectly to the item although he or she has mastered all required attributes; analyzed using the G-DINA model with 0 is low and 1 is high
cIndependent samples t-test with 0 = female, 1 = male; positive t-values represent higher mean scores for women than for men, negative t-values represent higher mean scores for men than for women
dLinear regression analysis with pu-GPA as independent variable and performance on each item as dependent variable. All significant results for pu-GPA are in favor of higher pu-GPAs
eLinear regression analysis with Age as independent variable and performance on each item as dependent variable; for item 6 on the V-SJT the older students had an advantage, while they had a disadvantage on item 2 of the written test