The third type of biased described by Burke and Eichler is the application of double standards. In other words, people are treated differently when they don’t actually require different treatment. For example, “most research on reproductive health issues and on everything related to parenting is done on women, even though men have separate and different reproductive health issues and typically also have a longer reproductive span than women” (Burke & Eichler, 2006: 10). In this instance, the needs and experiences of men are treated as less important than those of women.
Some of the research evidence on hip and knee replacement surgery suggests that physicians refer women for surgery less often than they refer men. The reasons for this difference are not entirely clear, though some studies have suggested that physicians may respond differently to male and female patients because they see men’s reports of pain as more significant and meaningful than women’s.
Source:  Burke, M.A., & Eichner, M. (2006). The BIAS FREE Framework a practical tool for identifying and eliminating social biases in health research. Geneve. Switzerland: Global Forum for Health Research, p.9., http://www.biasfree.org/full_BF.pdf