Bias may result from systematic errors in the research methodology.
Common types of bias:
- Only choose studies which they are familiar with or support their view-point
- Occurs when the two groups being compared differ systematically, eg. differences in the characteristics between those who are selected for a study.
Publication bias - Only select studies which have been published. In general, studies with statistically significant or positive results are more likely to be published than those with nonsignificant or negative results.(1)
Language bias - Only select studies written in English
Indexing bias - Only search a limited number of databases or use a limited choice of search terms.
1. Song F, Parekh S, Hooper L, et al. Dissemination and publication of research findings: an updated review of related biases. Health Technol Assess. 2010;14(8):iii, ix–xi, 1–193. doi: 10.3310/hta14080