Frequent food questionnaires FFQ are a simple way to obtain

Frequent food questionnaires (FFQ) are a simple way to obtain information on the foods individuals consume by asking them questions about typical amounts of food consumed in a day or week or month. A more accurate picture is obtained by obtaining a detailed food diary (DR) for several days, randomly chosen over a certain time period. The data obtained from a FFQ can be compared with the food diary to assess the validity of the questionnaire. The correlation between alcohol consumption from the food questionnaire and diary was r=0.89 based on seven individuals. Based on the seven individuals for whom data is available, which statement is INCORRECT?

DR                         FFQ

8.26                       1.68

0.83                       0

20.13                     15.1

11.16                      7.49

7.18                       12.84

1.76                        0

22.66                      25.06

a. because r>0, the amount that is truly consumed is always larger than what is stated on the FFQ

b. all of the answer options are correct.

c. the FFQ is a reasonable tool to obtain information on the amount of alcohol consumed by individuals.

d. typical consumption as stated on a FFQ is positively associated with what is actually consumed

Solution

a is incorrect.

Explanation: A positive correlation coefficient only implies that with change in DR readings, the FFQ readings will also change in the same manner. However, this does not reflect anything on the true consumed values, and therefore, we cannot judge whether the truly consumed amount will be larger or not.