 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 the 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 procedure or treatment. Random assignment, blinding, and controlling are key aspects of the design of experiments, as they help ensure that the results are not spurious or deceptive via confounding. This is why randomized controlled trials are vital in clinical research, especially ones that can be double-blinded and placebo-controlled. Mathematically, there are distinctions between randomization, pseudo-randomization, and quasi-randomization, as well as between random number generators and pseudo-random number generators. How much these differences matter in experiments such as clinical trials is a matter of trial design and statistical rigor, which affect evidence grading. Studies done with pseudo- or quasi-randomization are usually given nearly the same weight as those with true randomization but are viewed with a bit more caution.