There is little agreement on the philosophy of measuring clinical quality in health care. How data should be analyzed and transformed to healthcare information is an ongoing discussion. To accept a difference in quality between health departments as a real difference, one should consider to which extent the selection of patients, random variation, confounding and inconsistency may have influenced results. The aim of this article is to summarize aspects of clinical healthcare data analyses provided from the national clinical quality databases and to show how data may be presented in a way which is understandable to readers without specialised knowledge of statistics.