'''Random assignmentAssignment/Random''' '''placementPlacement''' is an [[experiment]]al technique for assigning [[human subject research|human participants]] or [[animal testing|animal subjects]] to different groups in an experiment, (e.g., [[treatment and control groups|a treatment group versus a control group]]) using [[wikt:randomization#Noun|randomization]], such as by a chance procedure such as [[coin flipping|flipping a coin]] or a [[random number generation|random number generator]].<ref name=":0">{{Cite book|last=Witte, Robert S.|url=https://www.worldcat.org/oclc/956984834|title=Statistics|publisher=|others=Witte, John S.|date=5 January 2017|isbn=978-1-119-25451-5|edition=11|___location=Hoboken, NJ|pages=5|oclc=956984834}}</ref> This ensures that each participant or subject has an equal chance of being placed in any group.<ref name=":0" /> Random assignment of participants helps to ensure that any differences between and within the groups are not [[systematic error|systematic]] at the outset of the experiment.<ref name=":0" /> Therefore, any differences between groups recorded at the end of the experiment can be more confidently attributed to the experimental procedures/treatment.<ref name=":0" />
Random assignment, [[blind experiment|blinding]], and [[scientific control|controlling]] are key aspects of the [[design of experiments]] because they help ensure that the results are not spurious or deceptive via [[confounding]]. This is why [[randomized controlled trial]]s are vital in [[clinical research]], especially ones that can be [[double-blinded]] and [[placebo-controlled]].
