Data collection mode may influence survey results. Examples of mode effects include the type of communication channel and the presence of an in-terviewer.

One considerable difference between CATI and CAWI is the don't know (DK) options. In our study, we try to find an equivalent way to present the DK option between CATI and CAWI questionnaires. The broader objective is to develop mixed-mode data collection for the Labour Force Survey (LFS).

In the Finnish LFS CATI questionnaire, the DK option is available for interviewers but they never offer it directly. Therefore, the presence and layout of the DK option in CAWI questionnaire has also been designed from that perspective.

By qualitative pre-testing (25-30 respondents), we study whether respondents need the DK option and if so, do they visually notice it while answering the CAWI questionnaire? This study will be completed by the end of April 2013.

In addition to qualitative pre-testing, we also carry out a web pilot study (a random sample of 6,000 Finns aged 16-64). In this study, we will have a split-ballot experiment to compare two different ways to present the DK option. Furthermore, the distribution of DK answers will be compared with the LFS CATI data collected at the same time. The data collection of the pilot study takes place in May 2013 and preliminary results will be ready in summer 2013.