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

GENESYS-IDplus
An enhanced screening service to identify and purge more non-productive numbers from your RDD samples, reducing data collection costs.


Background

As the pioneers in developing highly efficient RDD samples and generation systems, including the GENESYS Sampling System, GENESYS-Plus and GENESYS-ID products, Marketing Systems Group continually explores ways to increase the cost-effectiveness of random digit dialing (RDD) samples without compromising statistical integrity or alienating respondents through extensive intrusion into their households.

To address these concerns, we created GENESYS-ID ten years ago - an integrated, multiphase database, software and board-level hardware solution to identify non-productive numbers, thereby eliminating the costs associated with
interviewers needing to dial and disposition these numbers. Used by numerous commercial, government and academic institutions, this product has consistently identified 35-45% of non-productive phone numbers in GENESYS RDD samples, increasing production rates by about 10%.

However, due to qualitative differences in non-working intercept tones, variations in ring patterns, inconsistencies between incumbent and newer competitive local exchange carriers, telephone switching equipment, and our continued commitment to minimizing consumer intrusiveness, results vary significantly depending on the sample frame. In the Western US, for example, intercept cut-ins habitually occur much later in the ring cycle, resulting in fewer identified non-working numbers and lower productivity gains using traditional screening methods.

By recognizing and tracking these changes over the years, we have been able to identify problem areas, build a proprietary database and develop an enhanced GENESYS-ID process that significantly increases household hit rates for epsem RDD to the 75-80% range while still minimizing intrusiveness. Household hit rates for modified RDD samples are even higher.


The GENESYS-IDplus Process


The GENESYS-IDplus process builds on and incorporates many of the elements of the GENESYS-ID system. These include:

1. The Pre-Dialer Phase - The file of generated numbers is passed against the ID database, comprised of the GENESYS-Plus business database and the listed household database. Business numbers are eliminated while listed household numbers are set aside, to be recombined after the active Dialer Phase.

2. The Dialer Phase - The remaining numbers are then processed using automated dialing equipment - actually a specially configured PROYTY S Telephony system. In this phase, the dialing is 100% attended and the phone is allowed to ring up to two times. Specially trained agents are available to speak to anyone who might answer the phone and the number is dispositioned accordingly. Given this human intervention in evaluating all call results, virtually all remaining businesses and non-working and non-tritone intercepts, do compensate for differences in non-working intercept behavior. Most importantly, all of this testing takes place during the restricted hours of 9 a.m. - 5 p.m. local time, to further minimize intrusion since fewer people are home during these hours.

3. The Post-Dialer Phase - The sample is then reconstructed, excluding the non-productive numbers identified in the previous two phases.

Unlike other systems that rely solely on databases of non-working numbers that need constant updates, this methodology provides up-to-the-minute results since the sample is screened just a day or two prior to being utilized by your interviewers.

Again, given the importance of minimizing consumer intrusion, the number of rings is held to a minimum and the GENESYS-ID plus process is only used during restricted hours in local time zones. Also, since the majority of valid household numbers are identified and set aside during the initial Pre-Dialer Phase, actual household contacts are again minimized.

Utilization of this enhanced approach has demonstrated the capability of identifying a significant incremental amount of non-productive numbers - further increasing the household hit rate for the overall project. The result is a sample which retains all of the statistical integrity of an epsem RDD sample while nearly matching the cost-effectiveness of a listed frame.