The FREQ Procedure - SAS

1 SAS/STAT User s GuideThe freq ProcedureThis document is an individual chapter fromSAS/STAT User s correct bibliographic citation for the complete manual is as follows: SAS Institute Inc. User s , NC: SAS Institute 2013, SAS Institute Inc., Cary, NC, USAAll rights reserved. Produced in the United States of a hard-copy book: No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or byany means, electronic, mechanical, photocopying, or otherwise, without the prior written permission of the publisher, SAS a web download or e-book: Your use of this publication shall be governed by the terms established by the vendor at the timeyou acquire this scanning, uploading, and distribution of this book via the Internet or any other means without the permission of the publisher isillegal and punishable by law.

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4 Product or service names are registered trademarks or trademarks of SAS Institute Inc. in the USA and other countries. indicates USA registration. Other brand and product names are trademarks of their respective companies. 2013 SAS Institute Inc. All rights reserved. all that you need on your journey to knowledge and additional books and Greater Insight into Your SAS Software with SAS 40 The freq ProcedureContentsOverview: freq Procedure ..2622 Getting Started: freq Procedure ..2624 Frequency Tables and Statistics ..2624 Agreement Study ..2631 Syntax: freq Procedure ..2634 PROC freq Statement ..2634BY Statement ..2636 EXACT Statement ..2637 OUTPUT Statement.

5 2645 TABLES Statement ..2656 TEST Statement ..2693 WEIGHT Statement ..2696 Details: freq Procedure ..2697 Inputting Frequency Counts ..2697 Grouping with Formats ..2698 Missing Values ..2699In-Database Computation ..2701 Statistical Computations ..2702 Definitions and Notation ..2702 Chi-Square Tests and Statistics ..2704 Measures of Association ..2709 Binomial Proportion ..2719 Risks and Risk Differences ..2725 Common Risk Difference ..2736 Odds Ratio and Relative Risks for 2 x 2 Tables ..2737 Cochran-Armitage Test for Trend ..2740 Jonckheere-Terpstra Test ..2741 Tests and Measures of Agreement ..2743 Cochran-Mantel-Haenszel Statistics.

6 2748 Gail-Simon Test for Qualitative Interactions ..2756 Exact Statistics ..2757 Computational Resources ..2761 Output Data Sets ..2762 Displayed Output ..2765 ODS Table Names ..2773 ODS Graphics ..27772622 FChapter 40: The freq ProcedureExamples: freq Procedure ..2778 Example : Output Data Set of Frequencies ..2778 Example : Frequency Dot Plots ..2781 Example : Chi-Square Goodness-of-Fit Tests ..2784 Example : Binomial Proportions ..2788 Example : Analysis of a 2x2 Contingency Table ..2791 Example : Output Data Set of Chi-Square Statistics ..2794 Example : Cochran-Mantel-Haenszel Statistics ..2796 Example : Cochran-Armitage Trend Test.

7 2798 Example : Friedman s Chi-Square Test ..2802 Example : Cochran s Q Test ..2803 References ..2806 Overview: freq ProcedureThe freq Procedure produces one-way ton-way frequency and contingency (crosstabulation) tables. Fortwo-way tables, PROC freq computes tests and measures of association. Forn-way tables, PROC freq provides stratified analysis by computing statistics across, as well as within, one-way frequency tables, PROC freq computes goodness-of-fit tests for equal proportions or specifiednull proportions. For one-way tables, PROC freq also provides confidence limits and tests for binomialproportions, including tests for noninferiority and contingency tables, PROC freq can compute various statistics to examine the relationships betweentwo classification variables.

8 For some pairs of variables, you might want to examine the existence or strengthof any association between the variables. To determine if an association exists, chi-square tests are estimate the strength of an association, PROC freq computes measures of association that tend to beclose to zero when there is no association and close to the maximum (or minimum) value when there isperfect association. The statistics for contingency tables include the following: chi-square tests and measures measures of association risks (binomial proportions) and risk differences for2 2tables odds ratios and relative risks for2 2tables tests for trend tests and measures of agreement Cochran-Mantel-Haenszel statisticsOverview: freq ProcedureF2623 PROC freq computes asymptotic standard errors, confidence intervals, and tests for measures of associationand measures of agreement.

9 Exactp-values and confidence intervals are available for many test statisticsand measures. PROC freq also performs analyses that adjust for any stratification variables by computingstatistics across, as well as within, strata forn-way tables. These statistics include Cochran-Mantel-Haenszelstatistics and measures of choosing measures of association to use in analyzing a two-way table, you should consider the study design(which indicates whether the row and column variables are dependent or independent), the measurementscale of the variables (nominal, ordinal, or interval), the type of association that each measure is designedto detect, and any assumptions required for valid interpretation of a measure.

10 You should exercise care inselecting measures that are appropriate for your comments apply to the choice and interpretation of test statistics. For example, the Mantel-Haenszelchi-square statistic requires an ordinal scale for both variables and is designed to detect a linear Pearson chi-square, on the other hand, is appropriate for all variables and can detect any kind ofassociation, but it is less powerful for detecting a linear association because its power is dispersed over agreater number of degrees of freedom (except for2 2tables).For more information about selecting the appropriate statistical analyses, see Agresti (2007) and Stokes,Davis, and Koch (2012).