In this paper we show how one method of increasing the response rate, i.e. an extension of the fieldwork period, influences the structure of non-response and the differences between respondents and non-respondents. We used ...

In Poland, like in other countries, participation in surveys is declining over time. The growing non-response rates increase a risk of systematic bias of the results depending on the differences between non-respondents and ...

When we send advance letters to the sampled persons in a survey, we expect that the recipients will read them and, based on the information provided, will decide on their participation in the survey. Therefore, the letter ...