Random Assignment

Random assignment or random placement is an experimental technique for assigning subjects to different treatments (or no treatment). The thinking behind random assignment is that by randomizing treatment assignment, then the group attributes for the different treatments will be roughly equivalent and therefore any effect observed between treatment groups can be linked to the treatment effect and is not a characteristic of the individuals in the group.

In experimental design, random assignment of participants in experiments or treatment and control groups help to ensure that any differences between and within the groups are not systematic at the outset of the experiment. Random assignment does not guarantee that the groups are "matched" or equivalent, only that any differences are due to chance.

Random assignment facilitates comparison in experiments by creating similar groups. Example compares "Apple to Apple" and "Orange to Orange".

Random assignment

• Step 1: Begin with a collection of subjects. Example 20 people.
• Step 2: Devise a method to randomize that is purely mechanical ( e.g. flip a coin)
• Step 3: Assign subjects with "Heads" to one group : Control Group. Assign subjects with "Tails" to the other group: Experimental Group