Obviously, the reason behind the difference between distributions was not the type of phone but the fact that the respondents were different. Because of the more complicated life situation, people interviewed over mobile phones in the Labour Force Survey have to answer to more questions, e.g. about unemployment, seeking employment or about being in training. In the barometer survey the sample size was 1632 interviews. All respondents had to give answers to the same set of questions. In figure 3 are shown the distributions of the lengths of interviews in the barometer survey.
Distributions are nearly identical for both phone types.
In many countries, the growing popularity of mobile phones will have many different effects on the survey practice, on the survey quality, and on the expenses in all surveys where data is collected by interviews. At the moment, there is not much information on that area, yet. This study is a first attempt to shed some light on how mobile phones may affect the surveys. Clearly, more research that is thoroughgoing is needed. In order to have more accurate information, an especially for this purpose designed study is necessary.