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Epidemiology and Genomics Research Program

Converting Frequency Responses to Daily Frequency

Frequency information on the DSQ in NHANES 2009-2010 was collected using a rate and time unit (e.g., 3 times per week). A different response format consisting of a set number of frequency categories is used in the self-administered paper questionnaire. In both cases, the frequency responses are converted to a common unit of time, i.e. times per day.

For frequency category responses, we used the following conversions. Note that the frequency categories differ somewhat between foods and beverages.

Frequency Category Daily Frequency
Foods Beverages
Never 0 0
1 time last month 0.033 0.033
2-3 times last month 0.083 0.083
1 time per week 0.143 0.143
2 times per week 0.286 0.286
3-4 times per week 0.5 0.5
5-6 times per week 0.786 0.786
1 time per day 1 1
2 or more times per day 2 -
2-3 times per day - 2.5
4-5 times per day - 4.5
6 or more times per day - 6

If using the rate and time unit format, we used the following procedures:

Time Period Reported Daily Frequency
Day As reported
Week Reported frequency divided by 7
Month Reported frequency divided by 30