Red blood cell adhesion

Researchers into the genetic disease sickle cell anemia are interested in how red blood cells adhere to endothelial cells, which form the innermost lining of blood vessels. A set of 14 blood samples are obtained, and each sample is split in half. One half of the blood sample is profuse over an endothelial monolayer of type A and the other half of the blood sample is profused over an endothelial monolayer of type B. The two types differs in respect to the stimulation conditions of the endothelial cells. The data represent the number of adherent red blood cells per $\textrm{mm}^2$ .