A description of RDD and GENESYS-ID+ (The non-productive number purge) RDD Sample Methodology. The RDD sample that was utilized for this
project can be best characterized as a single stage epsem sample of all residential
telephone numbers (including listed, unlisted and non-published numbers) in
the defined sample frame. The
following paragraphs detail the underlying methodology. The system utilizes a database consisting of all
residential telephone exchanges, working bank information, and various
geographic service parameters such as state, county, Primary Zip code,
etc. In addition, the database
provides working bank information at the two-digit level - each of the 100
banks ( i.e., first two digits of the four-digit
suffix) in each exchange is defined as "working" if it contains one
or more listed telephone households.
On a National basis, this definition covers an estimated 96.4% of all
residential telephone numbers and 99.96% of listed residential numbers. This
database is updated on a quarterly basis. The sample frame consists of the set of all telephone
exchanges which meet the geographic criteria.
This geographic definition is made using one or more of the geographic
codes included in the database.
Following specification of the geographic area, the system selects all
exchanges and associated working banks which meet those criteria. Based on the sample frame defined above, the system computes an interval such that
the number of intervals is equivalent to the desired number of sample
pieces. The interval is computed by
dividing the total possible telephone numbers in the sample frame (i.e., # of
working banks X 100) by the number of RDD sample pieces required. Within each interval a single random number
is generated between 1 and the interval size; the corresponding phone number
within the interval is identified and written to an output file. The result, is that every
potential telephone number within the defined sample frame has a known and
equal probability of selection. GENESYS-ID+. This process is designed to purge a
percentage (approximately 75%) of two types of telephone numbers from the
sample--business and non-productive numbers.
Since this process is completed after the sample is generated, the
statistical integrity of the sample is maintained. To purge the business numbers, a database comprised of
non-residential yellow page businesses is utilized. The distinction of non-residential is important because over one million households nationwide use their residential phone number
for business purposes as well. The
generated sample is compared to this database, and any matching telephone
numbers are purged from the sample. The remaining numbers that are not purged from the sample
are then examined to determine if they are non-productive. |
RDD Methodology |