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Melanie Dove, MPH, ScD UC Davis

Melanie Dove, MPH, ScD UC Davis. Katherine Heck, MPH UC San Francisco. mdove@ucdavis.edu QSCERT-PC Postdoc, UCD Surveys: National Health and Nutrition Examination Survey (NHANES), California Health Interview Survey (CHIS) Previously: California Department of Public Health, CDC/NCHS.

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Melanie Dove, MPH, ScD UC Davis

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  1. Melanie Dove, MPH, ScD UC Davis Katherine Heck, MPH UC San Francisco mdove@ucdavis.edu • QSCERT-PC Postdoc, UCD • Surveys: National Health and Nutrition Examination Survey (NHANES), California Health Interview Survey (CHIS) • Previously: California Department of Public Health, CDC/NCHS Katherine.Heck@ucsf.edu • Research analyst, UCSF • Surveys: California Maternal and Infant Health Assessment (MIHA) survey, Listening to Mothers-CA • Previously: California Department of Public Health, CDC/NCHS

  2. Survey data analysis made easy with SAS Katherine Heck, MPH UC San Francisco Melanie Dove, MPH, ScD UC Davis

  3. Overview Background Survey design factors (weight and variance) How to analyze the data

  4. Surveys • Representativeness: Using a sample of individuals to represent a population

  5. Survey data • Different types: • Health, economic, marketing, sociology, psychology • Cross sectional • Data collection methods • In person, phone, mail, online

  6. California Health Interview Survey (CHIS) Health survey that represents California California’s population: 39,809,693 (1/1/2018) State of California, Department of Finance, E-1 Population Estimates for Cities, Counties and the State with Annual Percent Change — January 1, 2017 and 2018. Sacramento, California, May 2018.

  7. Sampling • Convenience • Simple random • Stratified

  8. Sampling • Cluster • within specified groups or geographic areas • sometimes called primary sampling units (PSUs) • Stratification • select a specified number of individuals from a particular population group • can be used for oversampling 

  9. Cluster Stratified

  10. Variance • Individuals within clusters are similar • Overestimate variance – significance • Need to account for the sample design if any stratification, clustering, or weighting was used

  11. Weighting Weight: a value indicating the number of people the respondent represents CA - 39,809,693 CHIS - 24,031 Weight

  12. Weights • Single weight variable -or- • Replicate weights, a series of weight variables which must be used in combination to correctly weight the sample

  13. SAS survey procedures SAS survey procedures: • ProcSurveyfreq: Frequencies, crosstabs • ProcSurveymeans: Means, medians • ProcSurveyreg: Linear regression • ProcSurveylogistic: Logistic regression • ProcSurveyphreg: Cox proportional hazards model • ProcSurveyselect: Sample selection Procedures can produce standard errors and confidence intervals

  14. Results with and without survey procedures: confidence intervals Example: CHIS, 2016 adult survey Weighted percent and confidence interval * Ever diagnosed with asthma, age 30-34 • ProcFreq results: 13.89% (13.85%-13.93%) • Proc Surveyfreq results: 13.89% (9.97%-17.80%)

  15. Survey components and syntax • Stratification: STRATA statement • Clustering: CLUSTER statement • Weighting: • Subpopulation analyses: DOMAIN statement or “flag” variables  • Do not use “where” to subset data WEIGHT statement (and REPWEIGHT if using replicate weights)

  16. Survey procedure examples

  17. Proc Surveyfreq - stratum/cluster proc surveyfreqdata=dataset varmethod=taylor; strata  stratum; clusterPSU; weight  weightvar; tablesagegrp; run; procfreqdata=dataset; tablesagegrp; run;

  18. Proc Surveyfreq - stratum/cluster Missing data proc surveyfreqnomcar data=dataset total=c.sampfrac; strata  stratum; clusterPSU; weight  weightvar; tablesagegrp * disease / row col cl; formatagegrpagegrpf.; run; Finite pop correction Confidence limits Row % Col %

  19. Proc Surveyfreq - replicate weights proc surveyfreqdata=dataset varmethod=jackknife; weight  weightvar; repweightwtvar1-wtvar80/JKCOEFS=1; tablesagegrp * disease / row cl ; formatagegrpagegrpf.; run; Variance estimation method Two weighting statements

  20. Libname statement libnameCHIS‘C:\HOW\Heck’; data adult; set chis.adult; run;

  21. CHIS age variable

  22. Proc Surveyfreq - age proc surveyfreqdata=adult varmethod= ?????; weight ????? ; repweight ?????/JKCOEFS=1; tables?????; run;

  23. Proc Surveyfreq - age proc surveyfreqdata=adult varmethod=jackknife; weight  rakedw0; repweightrakedw1-rakedw80/JKCOEFS=1; tables  srage_p1 / cl; run;

  24. Proc Surveyfreq - Results

  25. CHIS: Asthma variable

  26. Proc Surveyfreq syntax proc surveyfreqdata=adult varmethod=jackknife; weight ?????; repweight ????? / JKCOEFS=1 ; tables????? * ?????  / row cl nototal; run; Category (age) Outcome (asthma) No row/col totals

  27. Proc Surveyfreq syntax proc surveyfreqdata=c.adultvarmethod=jackknife; weight  rakedw0; repweightrakedw1-rakedw80 / JKCOEFS=1 ; tables  srage_p1 * ab17 / row cl nototal; run; Category (age) Outcome (asthma) No row/col totals

  28. Proc Surveyfreq output

  29. ProcSurveyfreq with chi-square proc surveyfreqdata=c.adultvarmethod=jackknife; weight  weightvar; repweightwtvar1-wtvar80 / JKCOEFS=1 ; tablessrsex * ab29 / row cl nototalchisq; run; Hypertension Gender Chi-square

  30. Proc Surveyfreqoutput

  31. Proc Surveymeans example CHIS 2016, number of times walked for leisure, past 7 days, by family type proc surveymeansdata=c.adultvarmethod=JACKKNIFE;  weight    rakedw0; repweight rakedw1-rakedw80 / JKCOEFS=1 ; var       AD41W ; domain    FAMT4 ; run; AD41W = how often walked Domain = group(s) of interest FAMT4 = family structure

  32. Results

  33. Proc Surveylogistic exampleUsual source of care by uninsured, adults 18-64, CHIS 2016 proc surveylogisticdata=adult varmethod=JACKKNIFE;  weight    rakedw0; repweight rakedw1-rakedw80/JKCOEFS=1; class     uninsured (ref='Insured'); modelnousual (descending) = uninsured ; format    uninsured unins.; run;

  34. Proc Surveylogistic results

  35. Resources to analyze CHIS data Analyze CHIS Data website: http://healthpolicy.ucla.edu/chis/analyze/Pages/default.aspx Webinar: http://www.authorstream.com/Presentation/mattjans-1668262-chis-data-analysis-webinar-recording/

  36. Thank you! Questions?

  37. Contact Information • Name: Melanie Dove • Company:  UC Davis • City/State:  Sacramento, CA • Phone: 916-734-8364 • Email: mdove@ucdavis.edu

  38. Contact Information • Name: Katherine Heck • Company: UCSF • City/State: San Francisco, CA • Phone: 530-219-8895 • Email: Katherine.Heck@ucsf.edu

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