Use the proc descript procedure to generate geometric means and specify the sample design using the design option WR (with replacement). The data statement refers to the permanent dataset, Phthalate_analysis_data, created in module 10. The option noprint is used to limit the output that is printed. The option notsorted is used since you did not use the SAS procedure proc sort to sort the dataset by strata (sdmvstra) and PSU (sdmvpsu). The atlevel=1 (strata) and atlevel=2 (PSU) are necessary to calculate the degrees of freedom for the t-statistic.

Use the nest statement with strata (sdmvstra) and PSU (sdmvpsu) to account for the design effects.

Use the weight statement to account for the unequal probability of sampling and non-response.  In this example, the 6-year Phthalate Subsample Weight  (WTSPH6YR) is used.

Use the subgroup statement lists the categorical variables for which statistics are requested. This example uses 5 age categories (age5cat), gender (riagendr), race-ethnicity (reth4cat) and survey cycle (sddsrvyr). These variables also appear in the table statement.

Use the levels statement to define the number of categories in each of the subgroup variables. The level must be an integer greater than 0. This example uses five age categories, two genders, three race-ethnicity groups and three survey cycles.

Use the var statement to name the variable(s) to be analyzed. In this example, the Mono-(2-ethyl)-hexyl phthalate variable (URXMHP) is used.

Use the table statement to specify tabulations for which estimates are requested. If a table statement is not present, a one—dimensional distribution is generated for each variable in the subgroup statement. In this example the estimates are for age categories (age5cat), gender (riagendr), race-ethnicity (reth4cat) and survey cycle (sddsrvyr).

output   nsum geomean segeomean atlev2 atlev1/ filename=out3d replace;

Use the output statement to create a dataset that can be used to calculate a 95% confidence interval for the geometric mean.

In this example, the sample size (nsum), geometric mean (geomean), standard error of the geometric mean (segeomean), PSU (atlev2) and strata (atlev1) are output to a dataset named out3d.

The replace option is necessary when creating a dataset in the output statement.

Note: For a complete list of statistics that can be requested on the output statement see SUDAAN Users Manual.

Use the rtitle statement to assign a heading for each page of output.

The run statement signifies the end of the procedure.

Create a new dataset (result1) to calculate the 95% confidence interval of the geometric mean. The keep statement indicates the variables that will be kept in the final dataset.

set   out3d;

The set statement sets the dataset that was created in the output statement above.

dfs=atlev2-atlev1;

Data step to calculate the degrees of freedom used with the t-statistic. Degrees of freedom are calculated by subtracting the strata (atlev1) from the PSU (atlev2).

L95CI_T=round(geomean+tinv(.025, dfs)*segeomean, .01);
U95CI_T=round(geomean+tinv(.975, dfs)*segeomean, .01);

Data step to calculate the lower (L95CI_T) and upper (U95CI_T) confidence interval of the geometric mean using the t-distribution (tinv) and the standard error of the geometric mean (segeomean) calculated in the proc descript procedure above.

length Analyte $24  Demo $16;

Use the length statement to define the lengths of new variables created in the data step.

if variable=1 then Analyte="MPH (ng/ml)";
if age5cat=0 then demo="All";
else if age5cat=1 then demo="6-11 years";
else if age5cat=2 then demo="12-19 years";
else if age5cat=3 then demo="20-40 years";
else if age5cat=4 then demo="40-59 years";
else if age5cat=5 then demo="60+ years";

if riagendr=1 then demo="Male";
else if riagendr=2 then demo="Female";

if reth4cat=1 then demo="NH white";
else if reth4cat=2 then demo="NH black";
else if reth4cat=3 then demo="Mexican American";

if sddsrvyr=1 then demo="99-00";
else if sddsrvyr=2 then demo="01-02"; else if sddsrvyr=3 then demo="03-04";

Define new variables using if/then statements.

Only select records where the demo variable is not equal (^=) to missing.

The run statement signifies the end of the data step.

Use proc print to view the results of the data step.

The id statement identifies the analyte and the demographic variable being displayed.

The var statement identifies the variables to be displayed in the output window.

The title statement assigns a heading for the output.

The footnote statement assigns a footnote for the output.

The run statement signifies the end of the procedure.