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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 |