This section describes how to use SAS to estimate mean nutrient intakes from supplements, along with standard errors. To illustrate this, consumption of supplemental calcium by females ages 20 and older is used as an example.

Use the PROC SURVEYMEANS procedure to compute properly weighted estimated means and standard errors.

In the sample below, the NOBS, MEAN, and STDERR options in the PROC SURVEYMEANS statement request that the number of observations, the estimated mean, and its estimated standard error, respectively, be printed for each analysis variable. The DOMAIN statement designates the combination of variables required to obtain separate estimates by the cohort of interest (INCOHF20) within each age group (AGEGRP). INCOHF20 is a variable that has value 1 if the individual is “in the cohort” and zero otherwise. Here, females ages 20 and older have INCOHF20=1. As in the SUDAAN example above, the weight variable being used is for the MEC subsample (WTMEC2YR).

*-------------------------------------------------------------------------;

* Use the PROC SURVEYMEANS procedure in SAS to estimate mean intakes
of ;

* calcium from supplements using complex survey design factors
(strata ;

* and
PSU)
;

*-------------------------------------------------------------------------;

strata
SDMVSTRA;

cluster SDMVPSU;

domain INCOHF20*AGEGRP;

var
DAILYAVG;

weight
WTMEC2YR;

format
AGEGRP
AGEGRP. ;

;

```
Data Summary
Number of Strata 15
Number of Clusters 30
Number of Observations 10122
Number of Observations Used 9643
Number of Obs with Nonpositive Weights 479
Sum of Weights 286222757
Statistics
Std Error
Variable N Mean of Mean
--------------------------------------------------------
DAILYAVG 9618 142.999400 9.643379
--------------------------------------------------------
Domain Analysis: Age of subject*INCOHF20
Age of Std Error
subject INCOHF20 Variable N Mean of Mean
-------------------------------------------------------------------------------
20-39 0 DAILYAVG 767 62.602567 6.471849
1 DAILYAVG 885 135.856261 17.035929
40-59 0 DAILYAVG 653 148.634197 17.715262
1 DAILYAVG 679 251.803537 23.644341
>= 60 0 DAILYAVG 849 197.511972 14.782058
1 DAILYAVG 898 426.392544 26.575240
-------------------------------------------------------------------------------
```

Highlights from the output include:

- 9,643 observations (respondents) were read by the program; 479 were skipped because their sampling weight value was zero (ineligible)
- 2,462 respondents were in the cohort; 885 were ages 20-39; 679 were ages 40-59; and 898 were ages 60 or older.
- Females ages 20-39 reported 136 mg, while those ages 40-59 reported 252 mg, and those ages 60 and older reported 426 mg. These are estimates of the population mean intake of supplemental calcium on a given day, which is equivalent to the mean usual intake of supplemental calcium for these age groups in the population.
- The standard errors of these means were 17.0, 23.6, and 26.6, respectively. See the NHANES Analytic Guidelines for more information on how to interpret standard errors.
- Unlike the SUDAAN output, the SAS output provides data for individuals who are not in the cohort. As we are not interested in those data, they can be ignored.

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