one mobile phone = one person? - european commission · (2007). reaching the u.s. cell phone...

One mobile phone = One person?

Consequences of cell phone sharing for sampling and weighting in mobile phone surveys

Outline:

1. Background

1Darmstadt University of Technology | Institute of Sociology | Research Methods | Dipl.-Soz. Britta Busse & Prof. Dr. Marek Fuchs

1. Background

2. Literature

3. Research questions

4. Methods

5. Results

6. Discussion

1. BackgroundOne mobile phone = one person?

Importance of cell phone studies for official statistics:

� telephone surveys as reliable, fast and cost-effective means for surveyseffective means for surveys

� already used for official statistics in Sweden, Estonia, Australia, Israel …

� rising mobile-only rates affect coverage

� mobile phone frame as supplement to landline telephone frame

2Darmstadt University of Technology | Institut fe of Sociology | Research Methods | Dipl.-Soz. Britta Busse & Prof. Dr. Marek Fuchs


Current method:

� mobile phone = personal device

� no sampling equivalent to within household selection selection

� no use of design weight regarding several persons using one mobile phone



Current calculation selection probability: (Gabler & Ayhan, 2007)

CC

FF m

km

k +•≈Π 1

→ Selection probability in cell phone frame depends only on number of cell phones the respondent owns


C

Ci

iF

Fii M

mk

zM

mk +•≈Π 1


Is it legitimate to calculate the selection Is it legitimate to calculate the selection probability in cell phone frames based on

this assumption?


2. LiteratureOne mobile phone = one person?

�50 validation interviews, US (Brick et al., 2007a) → 33% sharing

�176 US mobile-only household screening interviews (Brick et al., 2007b) → 8%interviews (Brick et al., 2007b) → 8%sharing

� 6,952 interviews in the 2007 BRFSS study (Link et al., 2007) → 15% sharing

�700 interviews in a German cross sectional study (Häder & Häder, 2009) → 8% sharing



Question wording as cause for differential rates:

�Question on household level

�Definition of “sharing”�Definition of “sharing”

�Sharing-questions might be perceived sensitive

�Focus on particular type of sharing only�Active vs. passive, hard vs. soft



Passive sharing

�Other people answer

calls on respondent’s

mobile phonemobile phone

Active sharing

�Respondent answers

calls on other people‘s

mobile phone


3. Research questionsOne mobile phone = one person?

�What is the prevalence of sharing in the German mobile phone population?

�Is the sharing population different from the �Is the sharing population different from the general mobile phone population?

�How to develop a design weight regarding sharing behavior?


4. MethodsOne mobile phone = one person?

�2 recruitment studies from a Mobile Phone Panel in Germany 2009 (1); 2010 (2)

�Sampling with Gabler-Häder Design in mobile phone and landline frame (1); Mobile phone phone and landline frame (1); Mobile phone frame only (2)

�Sample size: n=1,452 (1); n=1,426 (2)

�Response Rate: ?+27% (1); 15% (2)

�Samples weighted for mobile-only proportion


5. ResultsOne mobile phone = one person?

Prevalence of active sharing:

Active Sharing 2009

Active Sharing 2010

Yes, always 12% (85) 7% (91)


Yes, most of the time

12% (87) 13% (178)

Yes, seldom 20% (140) 26% (365)

No, never 51% (358) 53% (731)

Only when requested

5% (34) 2% (27)

Total 100% (704) 100% (1,392)


Prevalence of passive sharing:

Passive Sharing 2009

Passive Sharing 2010

Yes, always 12% (81) 8% (107)


Yes, most of the time

12% (87) 13% (187)

Yes, seldom 18% (130) 24% (338)

No, never 48% (341) 54% (748)

Only when requested

2% (12) 1% (11)

Total 100% (652) 100% (1,392)


Sociodemographics of active sharers:

Active Sharer2009 (n=1,088)

Active Sharer 2010 (n=957)

Sex (male) .85 .96

Age (z) .73** .93


Age (z) .73** .93

Education (High school) .95 .87

Occupation (yes) .63** .87

Income (<2,001 Euro) .73+ .75

Marital status (married) 1.81** 2.28***

Household size (z) 1.15 1.18+

Nagelkerke`s R2 .061 .069

+ p < .1; * p < .05; ** p < .01


Sociodemographics of passive sharers:

Passive Sharer2009 (n=1,088)

Passive Sharer2010 (n=957)

Sex (male) .72* .82

Age (z) .95 .71**


Age (z) .95 .71**

Education (High school) .67* 1.08

Occupation (yes) .77 .69+

Income (<2,001 Euro) .80 .74

Marital status (married) 1.80** 2.12***

Household size (z) 1.30** 1.21

Nagelkerke`s R2 .081 .071

+ p < .1; * p < .05; ** p < .01


Active sharers are:

�Younger

�Less often employed

�Living in high-income households�Living in high-income households

�More often married

�Living in multi-person households



Passive sharers are:

�Female

�Younger

�Less educated�Less educated

�Less often employed

�More often married

�Living in multi-person households


6. DiscussionOne mobile phone = one person?

Developing a design weight regarding sharing:

�DWi = Design weight ∑ =

=h

j

i

z

DW

1

11

�h = # of mobile phone numbers that can be used to reach a respondent

�zij = # of eligible potential respondents for a particular mobile phone number


∑ =jijz1


Developing a design weight regarding sharing:

Description of respondent(not necessarily owner of mobile

phone)

Design Weight


phone)

Owns 1 mobile phone, solely being used by himself

1.000

Owns 2 mobile phones, 1 being used alone, 1 being shared with spouse

0.667

Owns 2 mobile phones, both shared with one other person- takes calls on family cell phone

0.833

=

1

11

iDW

+=

2

1

1

11

iDW

++=

5

1

2

1

2

11

iDW


Developing a design weight regarding sharing with information on:

�Equal usage of the mobile phone among sharing partners?sharing partners?

�Exact frequency of behavior

�Typical behavior of respondent when reached on another phone if incoming call asks for survey participation



How to obtain this information?

�Assessment of introductory segment of mobile phone interview for indications of sharingsharing

�Respondent selection procedure: Random selection or asking for “owner” of mobile phone

�Necessary information in order to determine selection probabilities for each mobile phone owned by respondent


LiteratureOne mobile phone = One person?

Brick, J. M., Brick, P. D., Dipko, S., Presser, S., Tucker, C. & Yuan, Y. (2007a). Cell phone survey feasibility in the U.S.: Sampling and calling cell numbers versus landline numbers. Public Opinion Quarterly, 71 (1), 23 – 39.

Brick, J. M., Edwards, S. W. & Lee, S. (2007b). Sampling telephone numbers and adults, interview length, and weighting in the California Health Interview Survey Cell Phone Pilot Study. Public Opinion Quarterly, 71 (5), 793 – 813.

Gabler, S. & Ayhan, Ö. (2007). Gewichtung bei Erhebungen im Festnetz und Gabler, S. & Ayhan, Ö. (2007). Gewichtung bei Erhebungen im Festnetz und über Mobilfunk: Ein Dual Frame Ansatz. ZUMA Nachrichten Spezial 13: 39 – 46.

Häder, M. & Häder, S. (Eds.) (2009). Telefonbefragungen über das Mobilfunknetz. Wiesbaden: GWV

Link, M. W., Battaglia, M. P., Frankel, M., Osborn, L., & Mokdad, A. H. (2007). Reaching the U.S. cell phone generation. Comparison of cell phone survey results with an ongoing landline telephone survey. Public Opinion Quarterly, 71(5), 814-839.

Tucker, C., Brick, M. J. & Meekins, B. (2007). Household telephone service and usage patterns in the United States in 2004: Implications for telephone samples. Public Opinion Quarterly, 71 (1), 3 – 22.


Darmstadt University of TechnologyDepartment 02Institute of SociologyInstitute of SociologyResearch MethodsDipl.-Soz. Britta Busse

Residenzschloss S3|12 (Room 35/36)64283 Darmstadt

Tel.: +49 6151/16-64291Fax: +49 6151/16-72070

[email protected]

Thank You.

one mobile phone = one person? - european commission · (2007). reaching the u.s. cell phone...

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