1. RTI International is a trade name of Research Triangle Institute 6110 Executive Blvd. ■ Suite 902 ■ Rockville, Maryland, USA 27709 Phone 301-770-8229 e-mail dcreel@rti.org Panel Survey of Hospitals: Sampling and Estimation Challenges Darryl V. Creel Third International Conference on Establishment Surveys Montreal, Quebec, Canada June 18-21, 2007

2. Outline  Purpose of Survey  Survey Design  Frame Development  Substitution  Estimation

3. Purpose of the Survey  Level of Drug Use and Abuse  Monitor Drug Use and Abuse Changes over Time

4. Survey Design  Complete Survey Redesign (New Beginning 2004)  Start of a New Panel – Maximize Overlap with Previous Panel  Change in Stratification Scheme  Geography  Ownership  Size  Stratified SRS WOR of Hospitals  Review All Emergency Department Visits  Change in Case Eligibility  Annual Sample Updates to Account for New Hospitals  Change in Contractors

5. Survey Design  Possible Modification to the New Design  Could Not Review All Emergency Department Visits in Some Hospitals  Added a Second Stage of Sampling to the New Design  Select Days within Month to Review Emergency Department Visits for Eligible Cases  Retain Single-stage Design  Standard Errors – Worst Case Single-Stage SE 97% of Two- Stage SE  Computational Time – Single-Stage ~ 300 Observations Took 12 Minutes, Two-Stage ~ 70,000 Observations Took 31.5 Hours

6. Frame Development  American Hospital Association (AHA) Annual Survey Database  Good Coverage  Inaccuracies in the File  Incorrect FIPS Information Some for Counties in FL  Nonexistant Codes  Inaccuracies in the Documentation  Counts for Changes in the Population not Consistent  Only Use a Few Variables from AHA  Stratification  Eligibility Determination

7. Frame Development  Changes in Populations of Statistical Units (Struijs and Willeboordse)  Change of Characteristics  Change of Existence  Birth  Death  Change of Structure  Concentration  Merger  Takeover  Deconcentration  Break-Up  Split-Off  Restructuring  Track for Allocation Emergency Department Visits Counts

8. Substitution  Hospitals are Difficult to Recruit  Use Responding Not Sampled Hospitals from the Previous Panel for Nonresponding Sampled Hospitals in Current Panel until Number of Nonresponding Hospitals in Current Panel Decreases  Substitution Only Occurs within a Sampling Stratum, i.e., Same Geography, Ownership Category, and Size Category  Match Number of Emergency Department Visits as Closely as Possible

9. Estimation  Main Focus on Analysis of Trends  Drug Classification Scheme Changes Constantly  Apply Most Recent Classification Scheme Retrospectively for Trends

10. Estimation  Actual Zero Eligible Cases  Some Hospitals Not on Micro-data Set, i.e., No Eligible Cases Found at Hospital During Charts Review  Hospitals on Micro-data Set May Not Have Specific Drugs, e.g., PCP  Carries Through to Specific Analysis  Generate Data with a Zero Value  Statistician Involvement Across All Aspects of the Survey  SUDAAN – SAMPCNT Statement

11. Summary  Purpose of Survey  Survey Design  Frame Development  Substitution  Estimation  Statisticians Involved