column variable Formal or code 1-6 ID number XXXXX.XX 8-15 Saturated Fat ? DR(g) XXXXX.XX 17-24 Saturated Fat- FFQ(g) XXXXX.XX 26-33 Total fat- DR(g) XXXXX.XX 35-42 Total fat-FFQ(g) XXXXX.XX 44-51 Alcohol Consumption DR (oz.) XXXXX.XX 53-60 Alcohol Consumption FFQ(oz.) XXXXX.XX 62-70 Total Calories ?DR XXXXXX.XX 72-80 Total Calories FFQ XXXXXX.XX Question: 2.28 A Frequently used method for quantifying dietary intake is in the form of quintiles. Compute quintiles for each nutrient and each method of recording, and relate the nutrient composition for DR and FFQ using the quintile scales. (That is how does the quintile category based on DR related to the quintile category based on FFQ for the same individual?) Do you get the same impression about the concordance between DR and FFQ using quintiles as in Problem 2.27, in which raw ungrouped nutrient intake is considered? In nutritional epidemiology, it is customary to assess nutrient intake in relation to total caloric intake. One measure used to accomplish this is nutrient density, which is defined as 100% x(caloric intake of a nutrient/total caloric intake) For fat consumption, 1 g of fat is equivalent to 9 calories. ' 2.7) Use descriptive statistics to relate nutrient intake for the DR and FFQ. Do you think the FFQ is a reasonably accurate approximation to the DR? Why or why not? NOTE: The food frequency questionnaire (FFQ) is an instrument often used in dietary epidemiology to assess consumption of specific foods. A person is asked to write down the number of servings per day typically eaten in the past year of over 100 individual food items. A food composition table is then used to compute nutrient intakes (protein, fat, etc.) based on aggregating responses for individual foods, The FFQ is inexpensive to administer but is considered less accurate than the diet record (DR) (the gold standard of dietary epidemiology) For the DR, a participant writes down the amount of each specific food eaten over the past week in a food diary and a nutritionist using a special computer program computes nutrient intakes from the food diaries. This is a much more expensive method of dietary recording. To validate the FFQ, 173 nurses participating in the Nurses? health study completed 4 weeks of diet recording about equally spaced over a 12 month period and an FFQ at the end of diet recording. Data are presented in data set VALID.DAT on the Companion Website for saturated fat, to total fat, total alcohol consumption, and total caloric intake for both the DR and FFQ. For the DR, average nutrient intakes were computed over the 4 weeks of diet recording. The table show the format of this file.
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