CHOICE OF SAMPLING LANDLINE VS MOBILE

SAMPLE SOLUTIONS

01

IntroductionDual Frame ApproachDual Frame Approach refers to the methodology of combining landline and cell phone numbers

in order to account for the different mobile/landline penetration within a certain sampling frame.

Several methods do exist on how to actually use the framework, e.g. How to handle households

that own both landline and mobile telephones. Nevertheless, there are enough reasons to actually

avoid landline numbers and use mobile only, or a dual-frame approach

When what to use ?When clients think of targeting a population within an emerging market, we often receive RFQ´s for

landline numbers since the main advantage seems to be the possibility of geographic tracking, thus

where a person is located. However in some market, the advantages for mobile sample outweigh

its disadvantage. This paper will analyze when what to use.

About Sample SolutionsSample Solutions Europe is the premier global provider of sampling solutions for survey research.

SAMPLE SOLUTIONS EUROPE offers access to more than 50 million business-to-business records

for market research and can deliver RDD sample for over 25 markets. Sample Solutions Europe was

established by a group of people with decades of experience in the (telephonic) research indus-

try. The lack of local sampling knowledge from the main players in the sample industry (for RDD

sampling), and the lack of details when providing B2B sample, led to the establishment of Sample

Solutions Europe. We aim to provide better, and more detailed, sample, being it RDD or B2B, than

any other multi-market sample provider out there, at the best price-quality ratio possible. This

philosophy has lead to more and more clients from the international research industry finding their

way to Sample Solution Europe for their phone samples.

Some Mobile Myths

“Mobile phone numbers are more

costly and harder to reach, so why

use mobile?”

02

On first glance, it seems to be more expensive to use mobile sample for calling

rather than landline sample. Calling mobile phones is often more expensive than

calling landlines. Also, it takes roughly 6 times more (working) mobile numbers

to reach the same target interviews, compared to mobile numbers. Lastly, the

targeting by region is not always possible, making it difficult to fill regional quo-

tas, especially towards the end of a study.

Before deciding on the sample it is essential to first conduct a small research on

attributes of the target population. These factors are the local population data,

mobile penetration, landline penetration and geographic circumstances. A good

start is the CIA Worldfactbook which provides most of this data, an overview of

landline and mobile penetration is provided in Appendix A. Based upon the pen-

etration data for landline and mobile, an informed decision can be made what

source to use. Also a small excursion to numbering frames is needed.

Get the whole picture!

03

When looking at Ireland, initially one would estimate that in terms of landline

penetration (43%), it seems reasonable to conduct a study with landline numbers

only from a practical point of view (methodological is a whole other story, which

we won’t go into within this paper). However as a result of the deregulation of

the telecommunication sector in Ireland, the main provider Eircom has first of

all seen a decrease of landline penetration from 82% to 69% and the trend will

continue. Furthermore many landline users changed to different providers which

have different numbering blocks allocated.

Figure 1: Mobile and Landline Penetration for several sample countries

What to choose ?As a result the landline penetration per numbering block (eg. 1000) has been

fallen drastically and thus leads to a high percentage of dead (abandoned) num-

bers. Thus for call-centers not making use of predictive dialers it would be rec-

ommended to use mobile sample instead of landline numbers.

“There is no exact mathematical equation which indicates preference for landline or mobile sample.”_______________________________________________________________

_______________________________________________________________

This is due to the fact that when using auto-dialer or power dialer, a lot of calling

time is used for dialing numbers in a row, thus waiting for working numbers to

appear. With a predictive dialer several numbers are dialed in parallel thus sig-

nificantly reducing the waiting time for agents.

CASE STUDY MALAYSIA – REGIONAL DIFFERENCES

Another parameter which is important, is regional differences within a country.

Taking Malaysia as an example: initially we provided landline sample as request-

ed by the client. During the project however it turned out that in some regions

landline numbers were working well, while in others it was almost impossible to

use landlines. What were the reasons for this?

After a thorough analysis, it turned out that within urban areas many landline

connections were in fact used for internet connections, and thus yielding a high

number of non-working numbers which could not be identified by pre-screen-

ing. sented areas is then enabled to ensure a representative geographical spread.

04

Provider lookupsFurthermore in rural areas (were mobile communication was not fully estab-

lished), landline penetration was significantly higher. The last factor is that many

landline users within the rural areas actually abandoned the landline numbers

and thus further decreased the landline penetration, which further reduced the

amount the landline penetration in rural areas. In order to overcome these prob-

lems, it was decided to call on large scale with mobile phone numbers only

making use of a new technique called provider query lookup. This ensured a

high working rate of mobile phone numbers. Towards the end of a study when

quotas need to be filled, the landline sample for underrepresented areas is then

enabled to ensure a representative geographical spread.

MOBILE VERSUS LANDLINE SCREENINGSince RDD sample is randomly generated, there is always a large percentage

of dead numbers. Due to the different numbering block density, the fraction of

dead numbers varies. This is why the raw RDD sample is pulsed: in many Western

Countries, the filtering rate is between 30% and 50% (i.e. 30-50% of the num-

bers are screened out as non-working), thus leading to more effective landline

sample. However raw mobile phone pulsing only results in around 10% filtering

out of non-working numbers, this is why a provider lookup is used. The provider

lookup query indicates the following:

1. Is the SIM-card activated?

2. Is the number roaming?

3. Is the phone switched on?

4. Which provider is it?

05

06

Summing upThis enables to call mobile phone numbers which have been active and switched

on within the last 24 hours, leading to more efficient mobile sample to dial on.

This is why in many South-East Asian countries, it is preferred to call mobile

sample rather than landline sample since the screening rate is a lot higher with

mobile numbers, compared to landline. Another factor is that the telephony

costs per minute are almost the same for landlines and mobiles, as opposed to

Western Europe.

Conclusion on Sampling

There are several conclusions that we can draw from this paper. It is important

to take several factors into account before targeting a population:

- Dialing costs (landline vs. mobile), especially for longer interviews

- Landline vs. Mobile penetration rate

- Regional differences

- Numbering block penetration

- Target population (age, gender etc.)

- Screening Effectiveness

Obviously not all these factors are evident straight from a simple lookup. How-

ever we are there to help you out with any questions you have.

For any questions or enquiries it is possible to contact us via info@samplesolu-

tions.eu or me directly via carsten.broich@samplesolutions.eu

07

countries worldwide

>95Covering

Some facts about our RDD Sample

Sample variables

40Up to

Fastest turnaround:

30 minutes, when using our online ordering program.

RDD LANDLINE SAMPLEEfficient, Representative and Cost-EfficientRandom Digit Dialing, commonly known as RDD, is a very cost effective method for generating a

representative sample of households with fixed telephones. It is especially useful when No provision

for targeting within specific population groups is needed for example: Gender, income, geograph-

ical location or religion. Sample Solutions Europe has developed a highly accurate RDD procedure

while maintaining the representative proportion of the corresponding populations.

RDD MOBILE SAMPLEDo not miss the trend towards towards a mobile populationOur Mobile RDD sample is aligned with the provider share of each country, thus still providing a

representative spread of the target population. Furthermore it is possible via a provider lookup to

trach changes of the mobile provider. Our mobile RDD sample can be enriched with geodata using

a postcode linkage thus allowing geographic properties.

cleared3 monthsMobiles are

Facts about our mobile RDD sample

Countries worldwide

95Available in

Listed RDD for

65.000.000Households wordwide, ensuring perfectly targeted respondents.

08

09

Get in touch !Request some Trial Sample or ask for consultancyAt Sample Solutions we value long time relationships with our cleints. This is why we provide con-

sultancy on offline sampling and list features without any charge.

SAMPLE SOLUTIONS EUROPE offers access to more than 50 million business-to-business records

for market research and can deliver RDD sample for over 25 markets. Sample Solutions Europe was

established by a group of people with decades of experience in the (telephonic) research indus-

try. The lack of local sampling knowledge from the main players in the sample industry (for RDD

sampling), and the lack of details when providing B2B sample, led to the establishment of Sample

Solutions Europe.

We aim to provide better, and more detailed, sample, being it RDD or B2B, than any other

multi-market sample provider out there, at the best price-quality ratio possible. This philosophy has

lead to more and more clients from the international research industry finding their way to Sample

Solution Europe for their phone samples.

Contact: info@samplesolutions.eu

Sample Solutions EuropeGroothandelsgebouw3013 AP Rotterdam

NetherlandsTel: +31 88 1267800

info@samplesolutions.eu

SAMPLE SOLUTIONS