I understand your concern about the need for randomization and why it should be implemented at all.
First, randomization is a form of selection that is completely random in its selection process, meaning that if there are 1000 available participants to select from, you can randomly throw the names into some form of randomization tool, and select the first 100 names that come up, without any variables defining the selection process.
The benefits of randomization can be viewed as such: It eliminates biased selections, balances groups with respect to the known and unknown variables in the study, and tests the equality of treatments applied [Yal17].
Basically, randomizing your research allows for a more realistic approach to the data found during the study, as this data is being applied to a broader range of information to benefit others.
https://www.solvedcollegepapers.com/product/psy-510-psy510-psy-510-jon
https://www.solvedcollegepapers.com/product/psy-510-psy510-psy-510-1-2-sh
