The SURVEYFREQ Procedure

Confidence Limits for Totals

If you specify the CLWT option in the TABLES statement, PROC SURVEYFREQ computes confidence limits for the weighted frequencies (totals) in the crosstabulation tables.

For the total in table cell (r, c), the confidence limits are computed as

ModifyingAbove upper N With caret Subscript r c Baseline plus-or-minus left-parenthesis t Subscript d f comma alpha slash 2 Baseline times normal upper S normal t normal d normal upper E normal r normal r left-parenthesis ModifyingAbove upper N With caret Subscript r c Baseline right-parenthesis right-parenthesis

where ModifyingAbove upper N With caret Subscript r c is the estimate of the total frequency in table cell (r, c), normal upper S normal t normal d normal upper E normal r normal r left-parenthesis ModifyingAbove upper N With caret Subscript r c Baseline right-parenthesis is the standard error of the estimate, and t Subscript d f comma alpha slash 2 is the 100 left-parenthesis 1 minus alpha slash 2 right-parenthesisth percentile of the t distribution with df degrees of freedom. (For more information, see the section Degrees of Freedom.) The confidence level alpha is determined by the value of the ALPHA= option; by default, ALPHA=0.05, which produces 95% confidence limits.

The confidence limits for row totals, column totals, and the overall total are computed similarly to the confidence limits for table cell totals.

For each table request, PROC SURVEYFREQ produces a nondisplayed ODS table, "Table Summary," which contains the number of observations, strata, and clusters that are included in the analysis of the requested table. When you request confidence limits, the "Table Summary" data set also contains the degrees of freedom df and the value of t Subscript d f comma alpha slash 2 that is used to compute the confidence limits. For more information about this output data set, see Example 118.3.

Last updated: December 09, 2022