[The National Danish Survey of Patient Experiences has a small positive bias].

The response rate in The National Danish Survey of Patient Experiences in 2009 was 54%. In order to evaluate bias due to non-responders, The Unit of Patient-perceived Quality merged survey data and data on patient background from Statistics Denmark. The relationships between the responding patients' background and their answers to six questions in the survey questionnaire are estimated with logistic regression analysis and subsequently used for predicting the answers of the non-responders.