When a researcher assigns participants to either an experimental or a control group based on their last names, systematic differences between groups are created before the experiment even begins. This is a confounding variable referred to as _____
A)observer bias.
B)participant bias.
C)selection bias.
D)assignment bias.

Question

Quizplus · Accepted Answer

This is an example of selection bias, where participants are not randomly assigned to groups but rather based on a non-relevant factor such as their last name. This creates systematic differences between the groups before the experiment even begins, making it difficult to confidently interpret any subsequent group differences as being solely due to the experimental manipulation.

When a Researcher Assigns Participants to Either an Experimental or a Control