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Table 2 Measures of reproducibility for single questions about consumption frequency in the test and retest food frequency questionnaire (FFQ)

From: Test-retest reproducibility of a food frequency questionnaire (FFQ) and estimated effects on disease risk in the Norwegian Women and Cancer Study (NOWAC)

   Agreement, % Misclassification, % Symmetry of misclassification, % Kappa
Food item (response options) n Total Never/rarelya ± 1 Categ.b ± 2 Categ.b Extr.c Retest<Test Retest>Test Difference Simple Weighted
Potatoes (7) 1452 62 1 25 9 0.0 21 17 4 0.48 0.61
Carrots (7) 1406 43 1 42 11 0.0 35 22 13 0.30 0.54
Salad (7) 1169 41 3 41 12 0.0 22 37 -15 0.28 0.52
Swede (7) 1134 49 7 38 8 0.0 31 20 11 0.32 0.52
"Other vegetables" (7) 865 34 8 35 18 0.5 34 32 2 0.20 0.37
Oranges (7) 1107 39 5 34 20 0.1 50 12 38 0.25 0.47
"Other fruits" (7) 978 39 4 34 17 0.2 29 33 -4 0.25 0.42
Whole milk (6) 710 85 78 11 3 0.1 8 6 2 0.52 0.61
Meat, reindeer (6) 1339 86 75 11 1 0.6 8 6 2 0.58 0.57
Roast (beef, pork, lamb) (5) 1280 54 13 37 7 0.1 26 20 6 0.33 0.42
Meat, chops (5) 1301 62 10 35 4 0.0 15 24 -9 0.42 0.52
"Other meat dishes" (5) 921 40 11 41 15 0.2 31 28 3 0.21 0.32
Cod/coalfish/haddock/pollack (6) 1362 48 2 41 9 0.0 29 22 7 0.32 0.51
Salmon/trout (6) 1225 53 5 39 7 0.0 22 25 -3 0.35 0.48
Fish liver (5) 1229 78 43 18 3 0.2 12 10 2 0.68 0.77
Shellfish (4) 1374 70 35 27 2 0.1 13 17 -4 0.54 0.62
Beer (7) 1005 63 41 29 6 0.0 14 23 -9 0.46 0.61
Wine (7) 1137 46 13 40 13 0.0 19 35 -16 0.34 0.60
Chocolate (6) 1402 57 18 35 6 0.0 26 17 9 0.42 0.57
Cod liver oil capsules, winter (5) 156 76 3 13 3 5.1 9 15 -6 0.33 0.45
Cod liver oil capsules, rest of year (5) 130 69 15 12 4 11.5 15 16 -1 0.44 0.53
  1. aLowest response category in the FFQ, bCategories: ± 1 or ± 2 from the line of agreement in the contingency table
  2. cExtremes: test-retest responses in the lowest and highest categories