RDD telephone sample for nationally representative data
Random Digit Dialling (RDD) creates a probability-based sample for telephone-based population surveys. It gives households more of a chance of being reached, making it the right choice whenever representativeness is important. Norstat’s RDD telephone sample supports high-quality data collection in 190 countries across the world, from population surveys and opinion polls to social research.
RDD Portfolio
Three sample types to match your study
Our RDD services cover three distinct sample types: mobile, landline and dual-frame. Not all telephone studies need the same approach, but we make sure you have the right numbers for your target population from day one.
All three types share the same transparent methodology and enhanced filtering that removes disconnected numbers before they are added to the sample, so your telephone interviewers are dialling live numbers rather than working through dead ends.
Mobile sample
Reach people that landlines no longer reach
As more households across markets become mobile-only, mobile RDD has become the primary frame for national representative telephone data collection. Our mobile RDD sample covers 190 countries, and includes data such as network provider information. So you get genuine national reach for your population surveys.
Dual-Frame RDD sample
Reduce bias by covering mobile and landline
A dual-frame approach draws from both mobile and landline numbers in order to reduce coverage bias and improve the overall representativeness of the sample. In particular, some demographic groups are easier to reach through the landline frame. If you have a telephone survey that requires balanced demographic representation, dual-frame can often be the optimal sampling strategy.
Landline RDD sample
Fully geo-coded residential landline sample
For studies where residential landline coverage is suitable, particularly for older demographics or markets with a high landline penetration, our landline RDD sample delivers a geographically coded frame with business numbers removed. It supports high-quality data collection, so you can focus on the research.
How we generate RDD telephone sample
Every RDD sample we deliver is built following a clear four-step process: frame generation, sampling, execution, and quality checks. You will always know exactly which frame your sample came from and how it was constructed.
1
Sampling Frame
We build the sampling frame from every possible number combination within the country numbering plan, ensuring true probability coverage with no numbers systematically excluded.
2
Raw RDD Generation
The raw RDD telephone sample is generated according to your specifications, from national representative and geo-targeted to custom strata, before any filtering is applied.
3
Number Processing
We screen all generated numbers, removing disconnected or inactive numbers, to improve fieldwork efficiency from the outset.
4
Post-Processing QC
Strata inspection, coverage documentation and final quality checks are applied before delivery. Frame coverage, population data and potential bias information are included with every sample.
Check our RDD telephone sample coverage
Explore frame coverage data, known bias information and mobile and landline access data for any of the 190 countries in our RDD database before committing to a project.
What comes with every RDD telephone sample order
- Full country frame coverage documentation
- Potential coverage bias information
- Mobile and landline access data by country
- Methodology upon request
- Disconnected numbers removed before delivery
- Frame sizes and population data included
- 90% of orders delivered within 24-48 working hours
- ISO 27001 and ISO 20252 certified
RDD telephone sample for your next project
Telephone surveys have been a core method for population research for decades. It is especially suitable in markets where online panels lack coverage, in crisis situations, or where clients require probability-based sampling.
RDD telephone sample at a glance
150
million RDD records delivered
190
Countries covered
350
projects per year
Frequently Asked Questions
Common questions about RDD telephone sample and how it works.
A respondent asked where the data came from — what should I say?
Which countries do you cover for RDD telephone sample?
What is the difference between mobile RDD, landline RDD and dual-frame RDD?
How quickly is RDD telephone sample delivered?
Can RDD telephone sample be used for IVR or push-to-web projects?
Start your RDD telephone sample project today
Share your country coverage and study requirements and we’ll come back with frame coverage data and a sampling strategy.
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