The “Don’t Know” Option and the Outcomes of Opinion Polls

Single Wave Study

General Information

The “Don’t Know” Option and the Outcomes of Opinion Polls
Project Number
In February 2012, the LISS panel was presented the “Don’t know” experiment. This experiment focuses on the effects of different ways of offering the "Don’t know" option by answering the research question: How does the "Don’t know" option influence the results of specific questions and of a survey or opinion poll as a whole?
Longitudinal Type
Single Wave Study
Begin date
End date


Van De Maat, J.
© 2012 CentERdata
Funding Organization
CentERdata/MESS Project

Datasets and documentation

View Documentation

Codebook in English
Codebook in Dutch

Data Files

English SPSS file
English STATA file


Variable name Variable Label Variable Type
nomem_encrNumber of household member encryptedpreloaded
fu12a_mYear and month of the field work periodconstructed
fu12a001How the respondent was presented the ‘Don’t know’ option:constructed
fu12a002Participation in second experimentpreloaded
fu12a003Where would you position yourself on a line from 1 to 7, where 1 means that differences in income should increase and 7 means that they should decrease?directly measured
fu12a004"The statutory retirement age should remain at 65 years".directly measured
fu12a005"Social welfare benefits should be lowered so that people are stimulated to find a job".directly measured
fu12a006Where would you position yourself on a line from 1 to 7, where 1 means that euthanasia should be prohibited and 7 means that euthanasia should be permitted?directly measured
fu12a007"Adoption by homosexual couples should be possible".directly measured
fu12a008"It is a good thing that women can have their egg cells frozen so that they can have children at a later age".directly measured
fu12a009Where would you position yourself on a line from 1 to 7, where 1 means that ethnic minorities can retain their own culture and 7 means that they should fully adapt?directly measured
fu12a010"There are too many people of another nationality living in the Netherlands".directly measured
fu12a011"All people that have lived in the Netherlands illegally for a long time should be permitted to stay here".directly measured
fu12a012Where would you position yourself on a line from 1 to 7, where 1 means that European unification should go even further and 7 means that unification has already gone too far?directly measured
fu12a013"The Netherlands should spend more money on development aid".directly measured
fu12a014"The United Nations has too little power".directly measured
fu12a015"The Queen may only express government policy towards journalists".directly measured
fu12a016Are you for or against surrogate motherhood?directly measured
fu12a017Was it difficult to answer the questions?directly measured
fu12a018Were the questions sufficiently clear?directly measured
fu12a019Did the questionnaire get you thinking about things?directly measured
fu12a020Was it an interesting subject?directly measured
fu12a021Did you enjoy answering the questions?directly measured
fu12a022Starting date questionnaireconstructed
fu12a023Starting time questionnaireconstructed
fu12a024End date questionnaireconstructed
fu12a025End time questionnaireconstructed
fu12a026Duration in secondsderived


Questionnaire: Don’t Know Experiment

The questionnaire was originally conducted in Dutch.

Browse Don’t Know Experiment

Response Information

Response Overview
Selected number of household members: 7517 (100%)
Non-response: 1789 (23.8%)
Response: 5728 (76.2%)
Complete: 5725 (76.2%)
Incomplete: 3 (0.0%)
Collection Events
06-02-2012 to 28-02-2012
panel members with the age of 16 years or older.
Collection Mode
internet survey
Fieldwork Note
A reminder was sent twice to non-respondents.