Study designs, levels of evidence, and scientific bias
摘要
Bias should be taken into account when assessing clinical trials. It can occur in various forms in clinical studies and might influence the results in different directions. Bias can occur through the selection of study patients, the investigators, the type of data, and the analysis of the data. Different study types suffer from different potential biases. The aim of this paper is to describe common types of clinical trials and to illustrate their potential biases.