Final answer:
An evacuated glass tube with a lavender stopper is likely to contain blood plasma or serum, with serum being the liquid remaining after removal of coagulation factors through clotting and centrifugation.
Step-by-step explanation:
An evacuated glass tube with a lavender stopper typically contains either blood plasma or blood serum, depending on whether or not blood coagulation factors have been removed. Blood plasma includes these coagulation factors, whereas serum is the component of plasma that remains after blood clotting has occurred and coagulation factors have been removed. This serum can then be used for various diagnostic purposes, such as disease monitoring and blood typing. When a lab technician collects a blood sample in a glass tube and allows it to sit for about an hour, the clotting process occurs, and the cellular components can be centrifuged down, leaving the liquid serum on top.