A research design with some, but not all, of the characteristics of an experimental design. While comparison groups are available and maximum controls are used to minimize threats to validity, random selection is typically not possible or practical.
This procedure likewise attempts to establish a cause and effect relationship. It is very similar to experimental design except that other means are used to control extraneous sources of causality. See the Tool Kits on this web site for specific instructions.
A study that seems like an “experimental study” and is designed to be almost as powerful a test as if it were experimental, but the people studied are not put into their groups randomly and there is no “comparison or control group.