You can have a look at the German survey answers with all the graphs here. (indiesgogerman.com)
If the new question shows a reported turnout that is closer to the actual turnout, it is presumed that the new version succeeds in reducing lies and thus produces more accurate survey answers. (blog.politics.ox.ac.uk)
The researchers performed the study by collecting survey answers from an Internet - based questionnaire. (techtimes.com)