Table 3.
Test–retest reliability of a food-frequency questionnaire for adolescents
| FFQ1 | FFQ2 | |||||||
|---|---|---|---|---|---|---|---|---|
| Median | (P25, P75) | Median | (P25, P75) | Spearman r | p | CC% | GM% | |
| Dairy products (milk, yoghurt) | 624 | (274, 812) | 323 | (181, 673) | 0.522 | <0.001 | 55 | 14 |
| Eggs | 12 | (5, 19) | 12 | (5, 18) | 0.421 | 0.001 | 47 | 17 |
| Meat and poultry | 63 | (50, 88) | 56 | (44, 78) | 0.411 | 0.001 | 47 | 19 |
| Fish | 22 | (14, 32) | 15 | (10, 25) | 0.494 | <0.001 | 38 | 17 |
| Bread and cereals | 153 | (110, 220) | 152 | (80, 193) | 0.347 | 0.008 | 36 | 24 |
| Potatoes, fruits, and vegetables | 198 | (128, 270) | 158 | (112, 237) | 0.667 | <0.001 | 43 | 7 |
| Sugar, sweets, and snacks | 84 | (65, 106) | 71 | (51, 92) | 0.581 | <0.001 | 53 | 14 |
| Butter, margarine, and oils | 7 | (4, 16) | 7 | (3, 15) | 0.569 | <0.001 | 48 | 16 |
| Beverages (water, juice, sodas, tea, and coffee) | 926 | (769, 1,129) | 825 | (513, 1,009) | 0.669 | <0.001 | 52 | 9 |
Food intake (g/day) presented for main food groups (median, 25th and 75th percentile, Spearman correlation coefficient, percent correctly classified (CC) and grossly misclassified (GM) into quartiles of food intake) (n=58).