<Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (May 2016) (Learn how and when to remove this template message) </Td> </Tr> <Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> Random assignment or random placement is an experimental technique for assigning human participants or animal subjects to different groups in an experiment (e.g., a treatment group versus a control group) using randomization, such as by a chance procedure (e.g., flipping a coin) or a random number generator . This ensures that each participant or subject has an equal chance of being placed in any group . Random assignment of participants helps to ensure that any differences between and within the groups are not systematic at the outset of the experiment . Thus, any differences between groups recorded at the end of the experiment can be more confidently attributed to the experimental procedures or treatment . </P>

Match each of the steps in a randomized and controlled experiment with its underlying rationale