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TABLE B-3 Estimates of Within-Subject Variation in Intake, Expressed as Standard Deviation (SD)a and Coefficient of Variation (CV) for Vitamins and Minerals in Adolescents and Children

Nutrientb

Adolescents, Ages 9–18 y

Children, Ages 4–8 y

 

Females

(n = 1,002)

Males

(n = 998)

Females

(n = 817)

Males

(n = 883)

   

CV

 

CV

 

CV

 

CV

 

SD

(%)

SD

(%)

SD

(%)

SD

(%)

Vitamin A (μg)

852

109

898

91

808

103

723

86

Carotene (RE)

549

180

681

197

452

167

454

166

Vitamin E (mg)

4

67

5

62

3

54

3

57

Vitamin C (mg)

81

90

93

89

61

69

74

76

Thiamin (mg)

0.6

43

0.8

42

0.5

35

0.5

37

Riboflavin (mg)

0.7

42

1.0

41

0.6

35

0.7

35

Niacin (mg)

8

46

11

43

6

36

7

38

Vitamin B6 (μg)

0.7

49

1.0

49

0.6

42

0.7

43

Folate (μg)c

128

58

176

60

99

48

117

50

Vitamin B12 (μg)

5.5

142

5.0

93

9.6

254

4.7

118

Calcium (mg)

374

48

505

48

313

40

353

41

Phosphorous (mg)

410

38

542

37

321

32

352

32

Magnesium (mg)

86

41

109

39

61

31

71

33

Iron (mg)

6

47

9

50

5

45

6

43

Zinc (mg)

5

50

8

58

3

41

4

42

Copper (mg)

0.5

52

0.6

48

0.4

47

0.4

41

Sodium (mg)

1,313

45

1,630

42

930

38

957

35

Potassium (mg)

866

41

1,130

41

631

32

750

35

NOTE: When the CV is larger than 60 to 70 percent the distribution of daily intakes is nonnormal and the methods presented here are unreliable.

a Square root of the residual variance after accounting for subject, and sequence of observation (gender and age controlled by classifications).

b Nutrient intakes are for food only, data does not include intake from supplements.

c Folate reported in μg rather than as the new dietary folate equivalents (DFE).

SOURCE: Data from Continuing Survey of Food Intakes by Individuals1994–1996.

Note that D/SDD depends on the size of the difference between observed mean intake and the EAR and the standard deviation of that difference. For very large differences between observed mean intake and the EAR, it is likely that the ratio will exceed 1 and usual intake exceeds requirement. For smaller differences, the ability to critically interpret individual dietary intake data depends on the standard deviation of the difference between the observed intake



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