The post Week-weighted Averages in CANDAT appeared first on Food Intake Research.

]]>Rather than simply computing an average daily intake one may get more accurate results by weighting the days of the week and the weekend days differently.

A weight of 5 for each week day and a weight of 2 for weekend days should allow us to calculate week-weighted averages for any number of recalls. Of course, for recalls without weekends this would just be a day of the week average and vice-versa.

The week-weighted average could be calculated as follows:

x_{w} = (∑ w_{i} × x_{i}) ÷ ∑ w

where x_{w} is the weighted average with x_{i} as the daily intakes, and _{i} is 1 – 5 (codes for days of the week) or 0,6 codes for weekend days corresponding to Sunday and Saturday respectively. w_{1-5} would then be 5 and w_{0,6} would be 2.

with a variance of

Var(x_{w}) = Var(x) × ((∑ w_{i}^{2}) ÷ (w_{i})^{2})

where Var(x) would be the variance over all the days of the food intakes for the subject.

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]]>The post Nutrient data calculations appeared first on Food Intake Research.

]]>Nutrient databases express nutrient concentrations per 100 G. How many 100 Gs in one egg? Fortunately most nutrient databases also have food factors, in this case, small egg, average egg, large egg, etc. Each one of those has a factor. For instance if your egg is 60 G then your factor should be .6. The factor has to be .6 because that is what you multiply 100 G by to get 60 G. Hence all the of nutrient concentrations have to be multiplied by this same factor to yield the proper nutrient contribution. The protein for eggs in this case would be 2 (eggs) x .6 (factor) x [protein]. The square brackets around the nutrient denote concentration per 100 G. Simple? Of course it is.

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]]>The post Food data appeared first on Food Intake Research.

]]>In scientific studies with multiple coders of food data it is important to ensure consistency. When a subject mentions pasta as a consumed food, which, of multiple pasta codes must the coder use? Is more information required? A user manual which documents the decisions made during coding is essential. Coder training in the use of the manual is also essential.

The more accurate and consistent is the data coding and entry the more valuable will be the resulting data and the more likely will the study be able to show nutrient effects.

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