Table 1.

Validity: Variation in initial serving size and level of agreement between plate waste assessed by weight and the visual quarter-waste method for foods from 748 trays in 9 middle school and high school cafeterias in one Washington State school district during May 2014, by food type

	Agreement between Weight and Visual Quarter-Waste Method			Variation in Initial Serving Size
Food or beverage item Food: Entrees	n	κa	Standard errorbc	Standard deviation (g)d	Coefficient of variation (%)d
Hot dog	18	0.96	0.193
Cheese pizza	107	0.84	0.069
Fish taco	19	0.82	0.148
Canadian bacon and pineapple pizza	37	0.80	0.126
Seafood basket	56	0.80	0.095
Sub sandwich	72	0.75	0.077
Pepperoni pizza	57	0.74	0.100
Chicken tenders	67	0.64	0.084	13.1	16
Burger	26	0.59	0.153
Chicken Caesar entree salad	12	0.56	0.187
Food: Side items
Dinner roll	50	0.93	0.1101	1.36	3
Soup	58	0.92	0.095
Side fries	221	0.66	0.049	14.3	12
Fries with entree	108	0.63	0.067	19.3	16
Rice with entree	12	0.58	0.167
Food: Fruits and vegetables
Fruit cup	32	0.83	0.132	8.1	6
Potato salad	29	0.83	0.150	13.1	11
Fruit of the day	16	0.82	0.188
Baby carrots	53	0.82	0.096	2.6	4
Raisins	9	0.81	0.253	8.1	6
Grapes	10	0.80	0.283
Orange	17	0.80	0.217	17.4	10
Applesauce	30	0.79	0.132
Apple	61	0.79	0.088	8.6	7
Lettuce/tomato/pickle cup	22	0.77	0.138	8.0	11
Corn	12	0.73	0.191	6.6	8
Side salad	14	0.16	0.123	13.1	11
Beverages
Orange juice	109	0.85	0.073	0.9	1
Chocolate milk	333	0.83	0.041	1.4	1
White milk	114	0.83	0.070	1.3	0
Apple juice	388	0.82	0.038	1.5	1

^aMeasures the amount by which the agreement between two ratings exceeds that expected by chance. κ=1 when agreement is perfect and κ=0 when agreement is no better than chance.

^bBecause trays were randomly distributed to members of the research team, these standard errors do not account for differences between raters.

^cFor small numbers of pairs (<30) there is reduced confidence in the reliability of these standard errors.

^dTo examine the possibility of variation in initial serving sizes impacting validity analyses, standard deviations and coefficients of variation of “uneaten weight” measurement in grams was calculated for foods with at least four recorded weights for a whole, uneaten portion. These statistics are only related to one of the ratings, the gold standard weight, used to calculate the κ statistics. They are not related to the quarter-waste method rating.