Justification_B_SOE 2015 OMB Clearance

SUPPORTING STATEMENT FOR OMB CONTROL NUMBER 2900-0609, CONTINUED

STATISTICAL METHODS

VHA adjusts its oversampling and sampling distribution strategies each year to meet the needs of a changing Veteran population. The following gives an overview of statistical methods and the Methods report for the 2014 survey is included to assist in understanding the more nuanced changes that may occur year to year.

B-1: Respondent Universe and Respondent Selection Method

The Survey of Enrollee Universe is the population of Veterans enrolled in the VA health care system as of the end of the fiscal year preceding the survey administration. Enrollee records without a valid address or that are missing one of the stratification variables are not included. In addition, Veterans living outside the U.S. or Puerto Rico are also excluded from the sample.

B-2: Stratification Procedure

Traditionally, stratification variables have included VISN, whether the Veteran was grandfathered into the system during the 1999 enrollment reform (pre-enrollee) or enrolled after the reform (post-enrollee), and Veteran’s enrollment priority group. In 2008, VHA began oversampling the population of Veterans from Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND).

In 2014, VHA oversampled based on gender versus OEF/OIF/OND in order to collect stronger information regarding female Veterans. In addition, Veterans who had indicated they identified as Hispanic were oversampled in a supplemental sample of 2,625 interviews. Both of these populations are expected to be among the faster growing demographic groups in the population of enrolled Veterans.

In general, the target sample is distributed evenly among VISNs (2,000) per VISN, then pre- and post-enrollees, followed by distribution among priority groups. The exact distribution is dependent on oversampling requirements. In addition, while early versions of the survey required an emphasis on pre-enrollees for actuarial modelling purposes, this requirement is no longer critical and, therefore, over sampling of pre-enrollees will be phased out of the protocol.

For a sample size of approximately 42,000, we expect survey estimates based on the total sample to have error margins of approximately +/-0.5 percentage points at the 95 percent confidence level. For each priority level combining pre and post enrollees within VISN, with a sample size of approximately 200, we expect survey estimates to have error margins in the range of approximately +/-7 percentage points at the 95 percent confidence level. Confidence interval projections are based on measuring a population percentage equal to 50 percent. These projections do not account for sample design effects, which may increase the actual error margins for the survey estimates. VA will provide the contractor a list of enrollees from which to draw.

B-3 & B-4: Response Rate Maximization and Methodological Tests

Each year, VHA systematically conducts tests to refine the Survey of Enrollees in general and, specifically, the survey’s response rate. Key changes resulting from these tests include:

• A propensity score weighting adjustment to correct for differential non-response by health utilization and demographic information

• The introduction of pre-survey notification letters

• The introduction of a multi-mode survey instrument to increase response and cooperation rates and reduce response bias by reaching more enrollees who may have a different response pattern than those who reply to telephone surveys.

B-5: Consultants on statistical design

Gerard Benson, Director, Strategic Analysis Service (202-461-7084)

Office of Strategic Planning and Analysis

VHA Office of the Assistant Deputy Under Secretary for Health for Policy and Planning,

Department of Veterans Affairs

810 Vermont Avenue, NW

Washington, DC 20420

Laura Bowman, Survey Project Manager/Program Analyst, Strategic Analysis Service (Tel. 202-461-7108)

Office of Strategic Planning and Analysis

VHA Office of the Assistant Deputy Under Secretary for Health for Policy and Planning,

Department of Veterans Affairs

810 Vermont Avenue, NW

Washington, DC 20420

Mike Schwaber, Program Analyst, Strategic Analysis Service (Tel. 202-461-7108)

Office of Strategic Planning and Analysis

VHA Office of the Assistant Deputy Under Secretary for Health for Policy and Planning,

Department of Veterans Affairs

810 Vermont Avenue, NW

Washington, DC 20420

Contractor:

Westat

1600 Research Boulevard

Rockville, MD 20850

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