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Table 5 Agreement between reported and offered portion sizes as determined by the Kappa scores for portion size classification in quartiles, correlation coefficients and estimation bias for all, small and large portions

From: Validation of a newly automated web-based 24-hour dietary recall using fully controlled feeding studies

  Kappa score Correlation coefficient (P) Estimation bias (estimation error)a
All portions
N = 1373
0.62 0.80* 3.2 g (9.2%)
Small portions (<100 g)
N = 640
0.43 0.46* 7.6 g* (17.1%)
Large portions (≥100 g)
N = 733
0.50 0.68* −0.6 g (−2.4%)
  1. aEstimation bias: the average of the difference between reported and offered portion size. Estimation error: the mean ratio between the bias and the offered portion size
  2. *Significant at P < 0.05 (Difference between reported and offered portion was calculated to obtain the estimation bias)