0545 Health and Diet Survey SSB 2017 Extension

U.S. Food and Drug Administration
Health and Diet Survey
OMB Control No. 0910-0545
SUPPORTING STATEMENT Part B: Statistical Methods
1. Respondent Universe and Sampling Methods
The respondent universe for this collection of information will be non-institutionalized
adults 18 and older who speak English or Spanish. Within the sampling universe,
respondents will be randomly selected from two sampling frames: a national landline
telephone frame and a national cell phone frame. More specifically, the Health and Diet
Survey will adopt the overlapping dual frame approach as described by the American
Association for Public Opinion Research, i.e., we will select independent samples from
random-digit-dialing frames that overlap in their coverage (e.g., a landline frame and a cell
phone frame) and we will not screen out dual-frame prospective respondents (AAPOR
2010). Within a dual frame, we will include four groups of adults: (1) users o f landline
telephone only, (2) users of cell phone only, (3) dual users who use landline mainly, and (4)
dual users who use cell phone mainly.
For the landline interviews, households will be selected using a random-digit-dialing (RDD)
procedure by employing GENESYS, a database-assisted sampling methodology. The
GENESYS system uses a database of working residential telephone banks for the entire
United States to produce a single-stage random sample of residential telephone numbers.
RDD samples from the GENESYS system eliminate the reduction in precision caused by the
multi-stage cluster designs of traditional RDD procedures. GENESYS samples are widely
accepted because of their methodological rigor and efficiency.
The GENESYS database is constructed from three sources: a master list of area codeexchange combinations obtained from BELLCORE, a summary file of listed telephone
numbers in the United States obtained from Donnelly, and a summary file obtained from
CATI and other sources that cross-references zip codes to telephone exchanges. The
telephone numbers in these sources are matched and analyzed to produce a database of twodigit banks that contain at least 99 percent of the eligible telephone numbers in the U.S. (A
two-digit bank consists of the first eight digits of a 10-digit telephone number within which
up to 100 telephone numbers could be assigned, e.g. 123/456-78xx). The database is used to
generate a random sample in which every telephone number, whether listed or not, has an
equal probability of selection. The sample, unlike a traditional RDD sample, has no design
effect associated with clustering of telephone numbers within telephone exchanges.
Identification of the designated respondent (DR) will be achieved by the most recent
birthday method. Once household eligibility has been established, interviewers will ask to
speak with the adult household member who had the most recent birthday. The DR will be
selected prior to any questions about at-home status or availability of potential DR, and no

substitutions will be allowed. If the DR will be unavailable throughout the study period, the
household will become ineligible.
The survey will over-sample African-American and Hispanic populations by dividing the
landline telephone exchanges into three strata: a stratum of geographic areas with high
concentrations of African-American population, a stratum of geographic areas with high
concentrations of Hispanic population, and a stratum with the remainder of the U.S. The first
two strata will be sampled with higher rates. These sampling rates will be determined to
achieve the desired numbers of African-American and Hispanics based on estimated
incidences within each stratum. The final sample numbers for Hispanic and AfricanAmericans will occur at random from the sample without screening. The geographic areas
with higher African-American and Hispanic concentrations will be identified using
GENESYS. In addition to the landline telephone exchanges, we may also oversample cell
phone users because research indicates that proportionately more African-Americans and
Hispanics are cell phone users than other racial groups.
2. Procedures for the Collection of Information
The survey will be conducted by a contractor using computer-assisted telephone
interviewing (CATI) technology. Each landline interview will consist of two parts: the
household screener and the survey questions. The household screener will be used to locate
eligible households and to identify a designated respondent (DR) as described below. Only
one respondent per household will be interviewed. Each cell phone interview will only
include the survey questions and will not include any within-household eligibility screening.
Information will be collected by experienced and specifically trained telephone interviewers.
Quality control will be assured by periodic monitoring of on-going interviews throughout
the study. This monitoring replaces the previously used validation interview, which
required maintaining the name and telephone number of the respondent until the validation
interview could be completed.
3. Methods to Maximize Response Rates and Deal with Non-response
In an effort to increase response rate, we plan to take the following measures:
 send advance letters to those households whose addresses can be found to notify
them of the impending interview;
 make as many call attempts as needed, up to 30 call attempts for a landline
number and 5 call attempts for a cell phone number, to complete an interview;
 keep the length of the survey to an average of 15 minutes;
 allow a field period of 120 days;
 stagger calling in various times of the day and days of the week;
 send conversion letters to those who initially refuse the interview and use
conversion specialists to conduct conversion calls;
 use a Spanish questionnaire to accommodate respondents who do not speak
English;

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conduct a non-response study to identify potential non-response biases and adjust
estimates statistically, if necessary; and
regular and continuous monitoring of interviewer performance and address any
operational issues in a timely manner.
non-responders for whom an address match is available in advance of the
conversion attempt.

4. Test of Procedures or Methods to be Undertaken
Two types of tests of the collection procedure are planned to minimize collection burden on
respondents and improve quality of collected information.
We plan to conduct 18 cognitive interviews. The primary purpose of these interviews is to
understand the mental processes that respondents use to answer survey questions. We will
use cognitive interview findings to revise the draft questionnaire, if necessary and
appropriate.
The second type of tests is field pretests focusing more on the length of the questionnaire
and respondent burden in an environment as close as possible to the real interviews. The
data collection contractor will administer the full instrument by telephone to 200 randomlyselected adults shortly before OMB approval of the collection of information is expected.
Scheduling the pretests close to the beginning of data collection will gain efficiency by
using interviewer training for both the pretests and the complete data collection. The
pretests will also serve the purposes of addressing problems in respondent selection,
interviewer instructions, skip patterns, and design of the computer-assisted-telephoneinterview program.
5. Individuals Consulted on Statistical Aspects and Individuals Collecting and/or Analyzing
Data
A contractor will collect the information on behalf of the FDA. The contractor will be
tasked to provide statistical consultation to the survey. Analysis of the information will be
conducted primarily by staff on the Consumer Studies Team, Center for Food Safety and
Applied Nutrition, FDA.

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